When you can’t eat without breaking out in hives, having your ears puff up like muffins, or getting the collywobbles, obtaining an accurate diagnosis can calm your anxieties. I’m not saying that being diagnosed with a food allergy is cause to celebrate, but diagnosis is the first step to relief.
In this chapter, you take the first step on your diagnostic journey by completing a self-screening test. Although this test isn’t intended to be a self-diagnosis, it can assist you in deciding whether you need to visit your family physician or an allergist for a more thorough workup. The self-screening test also guides you through the process of logging information that can be very useful in your diagnosis.
With your self-screening test in hand, you and your doctor can then embark on your search for the offending food(s). To assist you, I provide plenty of guidance and tips on how to team up with your family physician (or pediatrician) and allergist to more effectively determine if you do, in fact, have a food allergy, and (if you do) expedite the process of identifying the food(s) that ail you without overly restricting your diet. I also show you the sorts of allergy tests and other diagnostic routines you can expect, so you won’t be taken off guard by any of your doctor’s recommendations.
Tip: In this chapter, I refer to many of the common symptoms of food allergy. For a more complete discussion of symptoms and possible causes, check out Chapter 2.
The path from the point at which you feel ill to the point at which you receive a diagnosis and treatment plan can be a long and winding road. To assist you in navigating that path, check out this eye-in-the-sky overview of the diagnostic process:
Warning: The journey from problem to solution often requires time, patience, and persistence. Don’t try to take a shortcut by reaching for untested, unproven alternative tests and treatments. See “Avoiding the untested and unproven,” later in this chapter, for details.
Funny thing about people in general (specifically men)—they don’t like going to the doctor. They often prefer to tough it out, hope it goes away, or convince themselves that the doctor “can’t do anything” rather than seek immediate medical care. With food allergies, however, avoiding the doctor can be dangerous, because the longer you tough it out without an accurate diagnosis, the more likely your reactions are going to increase both in frequency and severity.
Remember: Allergic reactions begin and intensify with increased exposure to allergenic foods. Early diagnosis and an effective treatment plan can not only make you feel better now but also prevent you from feeling much worse down the road.
If you or a loved one is experiencing mysterious symptoms, particularly a couple minutes to a couple hours after consuming food or beverages, you may have a food allergy. Complete the self-screening test shown below. This self-screening test serves three very important purposes:
Warning: This self-screening test is not a self-diagnosis. Identifying specific allergens is tricky, even for a well-trained and experienced allergist, and you may be allergic to multiple foods. In addition, other conditions can produce symptoms similar to those of allergic reactions. Use the self-screening test only as a tool to facilitate a professional medical diagnosis and treatment.
When you first suspect that you have any health problem, the first doctor you typically go to see is a general practitioner (GP for short)—your family physician, pediatrician, or internist. In the following sections, I reveal how a GP can and cannot help you with food allergies, when and how to request a referral to a food allergist, and how to avoid quacks who promise everything, deliver little or nothing, and often discourage you from seeking effective treatment.
In the case of food allergy, seeing your GP first is a good idea for the several reasons:
Some GPs know quite a bit about food allergies. Pediatricians may even know a bit more, because food allergy is most common in young children. So what’s your GP supposed to do? In the following sections, I describe the standard care you can expect from your GP. If you’re not receiving a standard level of care, express your expectations to your GP. If you’re still not satisfied, you may need to look for another doctor.
Remember: Most patients love their GP’s and are satisfied with the general care they provide, but the number one complaint I hear from patients is this: “How could my doctor (pediatricians included) have been so ignorant about food allergy?” Many patients report symptoms of food allergy to their GP’s for years before their GP’s take the reports seriously. (GP’s generally take reports of severe reactions seriously and refer patients to an allergist immediately, but they frequently miss the signs of more subtle reactions.)
The least your GP should do is ask you a lot of questions, record a detailed history of symptoms and what makes them better or worse, and determine the likelihood that you’re at risk for severe or life-threatening reactions—that is, whether you may have an IgE-mediated allergy, as described in Chapter 2. If your doctor suspects that you have an IgE-mediated allergy, she will likely take the following steps:
Warning: To err on the side of safety, assume that the next reaction is going to be more severe than the previous reaction and equip yourself to deal with it. Just because a child developed hives only on her face during her first reaction to milk or egg, you can’t assume that the next reaction is going to be of a comparable intensity.
Your GP may or may not decide to initiate allergy testing. Very few GP’s have the training or materials to perform skin tests, but any doctor can perform blood testing for allergies (see “Hunting for IgE with RASTs,” later in this Chapter). RAST (radioallergosorbent test) results can be very helpful in proving that the suspect food really triggered your reaction. However, searching for culprit foods with extensive panels of tests—that is, by ordering tests for hundreds of foods—is usually a huge waste of time and money and risks returning a number of false positive tests which only complicates the diagnosis.
If your doctor doesn’t suspect an IgE-mediated allergy, then she should attempt to determine whether the reaction represented some other type of food allergy or a nonallergic food reaction (a food intolerance, as explained in “Ruling out food intolerances,” later in this chapter). The diagnosis and management of non-IgE-mediated food allergy often requires the assistance of a gastroenterologist as well as an allergist. In some cases, the history may be insufficient for discerning the cause of a particular reaction. This is most often the case with patients who have isolated gastrointestinal symptoms. In such instances, your GP should arrange for further evaluation and proceed as if the reaction were IgE-mediated, including equipping you with epinephrine if suspicion is sufficiently high.
Based on your history and any test results, your GP should tell you which foods to avoid until further evaluation. Your doctor should carefully interpret the RASTs, since you can often test positive for safe foods, and you don’t want to be saddled with an overly restrictive diet. In some cases, a GP orders RASTs but is not fully competent in interpreting the results. Have your RAST results forwarded to the allergist you decide to see.
Remember: When you’re on an extremely restrictive diet, meeting your nutritional needs can be tough, especially for infants and children. If your doctor prescribes extreme restrictions, he’s likely to refer you to a nutritionist, as well. If he doesn’t refer you, request a referral, as explained in the section, “Navigating the referral process,” below.
You visited your GP, she took a detailed history, told you that you probably were suffering from a food allergy, and referred you to an allergist. Good for you. You’re now on your way to a more thorough workup and can skip ahead to the section, “Teaming up with your allergist for optimum results.” If, on the other hand, your GP offers no reasonable alternative diagnosis or effective treatment and is reluctant to refer you to an allergist, you may have to crank your efforts up a notch:
Tip: If you have to pay out of pocket for tests and treatments, mention this to your doctor. Doctors are human beings who are well aware of the high-cost of medical care. They may offer you a discount or be willing to set up a reasonable payment plan and will often be willing to charge you what they would normally get back from the insurance company (an average of a 36 percent discount).
In the not-so-good-old days, health insurance companies often set strict limitations on referrals. Sometimes they penalized GPs for sending too many patients to specialists or offered rewards to GPs who issued fewer referrals. (In the real old days, prior to 1990, GP’s didn’t need to worry about this nonsense.) Fortunately, most insurance companies have ended their Draconian policies and now give their doctors carte blanche to make as many referrals as necessary. Some companies don’t even require referrals, so patients are free to see whichever doctor they deem most helpful.
If your GP seems reluctant to refer you to an allergist, don’t be quick to blame your insurance company. In most cases, your GP’s reluctance is based more on the fact that your GP really does not believe that you have a food allergy. If your doctor is unwilling to assist you in obtaining a referral to an allergist, become more proactive. Contact an allergist yourself, and see if your allergist can obtain the insurance approval you need.
Remember: GPs often have the mistaken notion that allergists can’t perform allergy tests on children until they’re two or three years old. This is clearly wrong. The consensus of food allergists is that the GP should make the referral as soon as possible after concerns of food allergy arise, even in a two- or three-month-old. The medical community has plenty of evidence that early diagnosis and treatment greatly benefit children and their families.
Alternative therapies for food allergies abound. Chiropractors, nutritionists, acupuncturists, and a variety of other alternative practitioners claim the ability to diagnose and treat food allergies. Some of these healthcare providers may even be quite knowledgeable about food allergies and beneficial in your care. Other practitioners who are more on the fringe or way out there, tout their snake-oils, magic potions, crystals, and other treatments that range from entertaining diversions to dangerous delusions.
Warning: Don’t fall for pumped-up promises of miracle cures. Seek well-trained, qualified medical practitioners to diagnose and manage your food allergies. If you do decide to pursue alternative routes—a chiropractor with an interest in food allergy, for example—I always advise that you see a traditional allergist as well. For details about the most common quack tests and treatments, skip to Chapter 8.
Your doctor decided to call in an allergist, or you decided on your own to pursue this option. Now you’re in the market for a top-notch allergist. But what exactly qualifies an allergist as top-notch? Here are the qualities to look for in an allergist:
In the following sections, I show you how to track down an ideal (or at least close-to-ideal) allergist and team up with your allergist to obtain the most accurate diagnosis and most effective treatment plan.
Tracking down a local allergist who’s best qualified to diagnose and treat food allergies is a four-step process:
The following sections explain each step in greater detail.
Your first recommendation typically comes from your GP. Your GP should be familiar with the allergists in your area, hopefully knows which allergists have expertise in food allergy, and may even know who would be the best fit from a style and personality standpoint.
If your GP doesn’t recommend a suitable allergist or you want additional input, ask everyone you know and trust, especially friends and family members who’ve already seen an allergist. Ask other doctors if you happen to know any. These people are often even more capable than your GP in helping you find the perfect doctor.
Tip: If you’re in a food-allergy support group, which isn’t likely at this point because you’re just getting started, recommendations from fellow members are pure gold. People often change allergists later based on recommendations from other members of the group.
Now that you have a long list of candidates, you can start paring down your list by crossing off any allergists not covered on your insurance policy. To see if a particular doctor participates in your insurance network, do one of the following:
When your GP refers you to an allergist, ask about the allergist’s credentials and bedside manner to learn as much as possible about his training and experience. If your GP is less than forthcoming or you obtained a recommendation from someone who has little solid information, the following organizations can help you gather information and can even provide you with additional names if you’ve come up short after talking to your GP, friends, and family:
Tip: Other local medical societies may be able to provide additional recommendations.
Rank the allergists on your list from first choice to last choice based on qualifications, reputation, and location, and then start calling around to make an appointment. Unfortunately, many allergists have a long waiting list, often several months. If you feel that you can’t wait that long, you may need to go with your second or third choice.
Still having trouble getting in to see the allergist? Here are some tips and tricks from seasoned patients:
Tip: After you see your allergist for the first time and assuming you’re happy with the allergist, don’t leave the office without setting up at least one appointment in advance. This can trim your wait time in the future. If you don’t need the appointment, cancel it a week or so in advance as a courtesy to other needy patients.
No matter what kind of healthcare issue you have, you get the best results when you team up with your doctor. To effectively team up with your allergist, here’s what you do:
Diagnosing a food allergy is about as challenging as finding an allergist who can see you the next day. Your allergist is likely to take a detailed history, perform a physical examination, and proceed with a battery of diagnostic tests to figure out what’s going on and which foods are the prime suspects.
Remember: The diagnostic process is more complicated if your food allergy is not IgE-mediated, since the most common allergy tests—skin tests and RASTs—both rely on the presence of IgE antibodies. These tests are useless in diagnosing non-IgE mediated food allergies.
In the following sections, I lead you through the diagnostic process step-by-step, so you know what to expect along the way.
Your medical history is of tremendous value in diagnosing food allergy, so don’t forget to bring the self-screening test you completed in the section “Self-Screening for Food Allergies,” to your first appointment. In addition to what you’ve already recorded, your allergist is likely to ask you a series of probing questions to determine whether true food allergy is likely, and whether the allergy is likely to be IgE mediated.
You can prepare for the doctor to review your medical history by jotting down your answers to the following questions:
Using your answers to these questions, your allergist formulates your medical history—one of the most important and useful diagnostic tools. Your allergist may also ask you to keep a food diary to find out even more about your diet and symptoms in an attempt to identify any consistent pattern to your reactions.
Although your history is the most important diagnostic tool, its usefulness varies depending on the results. Typically, the history leads to one of the following two common scenarios:
Remember: Several studies show that further testing confirms a history of suspected food allergy only about 30 to 40 percent of the time. Your allergist must interpret your history, including food diaries, with great caution.
You could place a pretty safe bet that by the time you get in to see the allergist, your symptoms will have magically disappeared. Your allergist asks to see the hives, and your skin is perfectly clear. Your tummy which was as bloated as a beach ball two days ago is as flat as an ironing board today. Even your sinuses are clear.
Even so, your allergist is going to perform a physical exam to look for signs of a possible food allergy, such as eczema and other rashes and symptoms of other allergic reactions, such as hay fever. What does hay fever have to do with food allergies? Well, food allergy is more likely to occur in those who have other types of allergy, and this can be an important clue.
Remember: The physical exam, in and of itself, is not always conclusive. Your exam may reveal no abnormalities, even if you have severe reactions to multiple foods. After all, the only good thing about food allergy is that you usually look and feel fine as long as you’re abstaining from the problem foods. One important bit of information a normal exam provides is that it reassures you and your allergist that you’re probably okay with your current diet.
Once your allergist commences testing, you may begin to wonder if you mistakenly stepped into the acupuncturist’s office. Allergists commonly perform skin-prick tests in which they poke or scratch the skin with an extract of the suspect food and observe any reactions on the surface of the skin. Your allergist may use any of the following three methods:
A positive skin test results in a mosquito bite-like reaction at the site of the test within minutes, indicating the presence of histamine, which causes the skin to swell. After 10-15 minutes, your allergist takes a reading and compares all tests to a control prick (to test your reaction to salt water, which shouldn’t cause a reaction). A larger reaction—a larger bump on your skin—typically shows an increased likelihood that you’re allergic to the tested food.
How many times can you expect to get poked? If you’re presenting symptoms of a nonfood allergy, such as hay fever or asthma, your allergist performs a fairly standard set of tests consisting of 20 to 40 skin pricks.
With food allergy the number of tests is typically based on patient history, so you can’t expect a set number. An allergist usually performs skin prick tests for only suspect foods. If you’ve had only one reaction to milk, for example, your allergist is likely to test only for milk to confirm suspicions. If the history identifies no particular problem food—you have eczema, for instance, but no specific food reactions—then, your allergist is likely to test for only the five or six most common food allergens, including milk, egg, soy, wheat, and peanut.
Warning: Be cautious of any allergist who recommends dozens of tests for food allergies. A few allergists out there routinely test every patient who walks into their office for 120 different foods, even if they have no reason to suspect a food allergy. Studies show that in children with eczema, if the skin prick tests or RASTs results are negative for the most common food allergens, the children are highly unlikely to be allergic to less common allergens.
Interpreting a skin test seems like a snap. Either it’s positive or negative. What’s so tricky about that? Actually, it’s tougher than it sounds.
The easiest result to interpret is when the test is completely negative. When you test negative for a particular food, the likelihood that you have an IgE-mediated reaction to that food is next to nothing. The main exceptions occur in babies in the first six to nine months of life, during which time occasional false negatives occur.
Remember: Skin tests are positive only if you have IgE antibodies to the food being tested. Skin tests do not detect non-IgE mediated allergies.
Interpreting positive food skin test results is more problematic. Positive tests indicate that IgE is present but do not, without confirmation from other sources, prove that a reaction will occur when you eat the food. In other words, the test can show a positive result or a false positive (a skin reaction even though you don’t react to the food when you eat it). False positives occur in the following scenarios:
Remember: Take the results of skin tests with a dose of salt. Overall, up to 60 percent of all positive food skin tests turn out to be incorrect (falsely positive) upon further evaluation. Some studies show that the larger the skin test (the bigger the bump on your skin at the site of the test), the more likely a true allergy is at work, although this has not proven true in other studies. Skin test results are only one component of the diagnostic picture, allergists should evaluate them carefully and in the context of the big, clinical picture, as demonstrated in the following sidebar.
Skin tests alone rarely prove much of anything. In a single week, I saw three patients, all of whom were diagnosed with egg allergy and came to me for a second opinion. Each had tested positively and had reactions of similar size to egg. Their cases illustrate the complexities of interpreting skin tests:
Cross-reactivity can occur when your immune system confuses one protein for another one. This typically happens with members of the same food family, but can occur between two allergens you may not imagine are related. A person who’s allergic to tree pollen, for example, may not be able to eat apples or cherries. Someone who’s allergic to ragweed may be sensitive to cantaloupe or banana.
Allergists remain vigilant of cross reactivity for two reasons:
Remember: When evaluating skin tests, your doctor needs to be aware of the possibility of cross reactivity, because the test may return a false positive result for a food you can safely eat.
Allergy skin testing is generally a very safe procedure. However, because it exposes you to a food that you may be highly allergic to, caution is always in order. An occasional patient may in fact be considered too allergic for administering a safe skin test. Incidence of systemic (whole body) reactions, however, are very low—estimates run at about 30 reactions per 100,000 tests.
Warning: Only allergists trained in the treatment of severe allergic reactions should perform skin tests, just in case you experience a severe reaction. Your allergist must have emergency equipment and drugs on hand for the treatment of anaphylaxis whenever performing a skin test. Chapter 2 provides more detailed information on anaphylaxis.
Another test that requires a needle is the RAST, a test that measures the amount of allergen-specific IgE in your blood. This test doesn’t require an allergist; your GP can perform the test, but an allergist may be more qualified to interpret the results and is usually the doctor who performs the test. RAST consists of drawing a small amount of blood and then having the blood tested—by sending it out to a lab. Doctors can perform RASTs for almost any food or airborne allergen.
RAST (short for radioallergosorbent test) is a term that actually refers to an older test method, one that allergists rarely use any more. The term stuck, however, and doctors still commonly the term to describe all of the test methods that measure specific IgE antibodies in the blood. A more accurate term would be immunoassay for specific IgE but I use RAST throughout the book, because it’s more common and a heck of a lot easier to type.
Remember: The most important point about RASTs is that they’re not all the same. Some types of RASTs are more accurate than others, and the results of one type of RAST are not interchangeable with the results of another type. For diagnosing food allergies, the type of RAST that has the best track record is the Pharmacia CAP fluorescent enzyme immunoassay. Wrap your mouth around that one! To simplify the nomenclature, doctors refer to this type of RAST as CAP-FEIA or CAP-RAST.
As with skin testing, negative RAST results are quite accurate in ruling out an IgE-mediated food allergy, but positive RAST results do not necessarily mean you have a true food allergy. False positive results occur with RASTs for the very same reasons they occur with skin testing. However, because the RAST is more of a true measure of the amount of IgE in your system, differentiating a true positive test from a false positive test is generally easier than it is in the case of skin tests.
When your doctor gets the results, she looks at your RAST score and interprets the results based on the following criteria:
Tip: Your doctor can often use RAST results to track your levels of specific IgE antibodies over time. RAST levels that decrease over time are an excellent indication that you’re outgrowing your allergy to a particular food. My colleagues and I typically decide when to try to re-introduce a food into a patient’s diet based on the RAST result. (See Chapter 15 for details about outgrowing food allergies.)
As you probably realized by now, neither skin tests nor RASTs are the perfect tests. Results can range from highly successful at best, to inconclusive, to misleading at worse. When discussing with your doctor which test would be most useful in your case, weigh the pros and cons of each.
Skin tests have a couple advantages over RASTs:
RASTs have several advantages over skin testing:
Remember: Neither skin-test nor RAST results are very good at predicting the type or severity of an allergic reaction. Although higher RAST levels generally indicate more severe reactions, numerous exceptions prevent RAST results from functioning as accurate predictors of a future reaction. This is due in part to the dose effect described in Chapter 3, but even with the same dose (amount of a problem food) three people with the same skin-test or RAST result may have hugely different reactions with exposure to the food. One person may eat peanuts regularly without symptoms, the second may experience minor hives, and the third may experience severe anaphylaxis.
You’ve been interviewed, examined, and poked, and your allergist can provide you with no definitive diagnosis. It happens, especially when you’re experiencing delayed reactions. Hope, however, remains. Your doctor has some additional tricks up his sleeve, including both eating the food (a food challenge) and not eating the food (an elimination diet). The following sections present additional diagnostic tools that can dig below the skin to unearth more mysterious causes.
When your allergies prove too elusive for skin tests and RASTs, your doctor may try to dare the allergies out of hiding by challenging them to react to suspect foods. This test, commonly called an oral food challenge, consists of feeding you increasing amounts of the suspect food under your doctor’s supervision, while observing you for symptoms. Food challenges are considered the only foolproof test for most food allergies. In addition to identifying elusive allergies, food challenges serve three useful purposes:
Warning: Don’t try this at home. Food challenges carry a risk of serious reactions. Only trained personnel with emergency treatment immediately available should perform these tests.
Your doctor can choose to perform a food challenge using either of the following three methods:
The ideal way to perform a food challenge test is to do a “double-blind, placebo-controlled challenge.” With this method, neither the allergist nor the patient is aware of which capsule or food contains the suspected allergen. In order for the test to be effective, you must also take capsules or eat food that does not contain the allergen (placebos). This ensures that any observed reaction is due to the allergen and not some other factor, such as stress or anxiety.
My colleagues and I often struggle to determine the right time to do a food challenge, especially to see if a patient has outgrown an allergy. If a patient has not experienced any recent reactions (recent reactions would guarantee that the patient is still allergic), we base most food challenge decisions on the CAP-RAST IgE level. If the CAP-RAST IgE level is low enough, we decide to move forward with a food challenge to verify that the patient has really outgrown the allergy.
A few years ago we published our experience with this method and were able to more clearly define the IgE levels at which a challenge may be reasonable. After all, we do not want to take the risk of a challenge if the odds of success are too small, but yet don’t want to restrict the diet more than necessary. In our study, we reported on 604 food challenges in 391 children to the five most common food allergens. Our goal was to establish the IgE level at which we could expect a 50 percent pass rate, and we determined a cutoff level of 2 kUA/L (kili-units per liter) for milk, egg, and peanut. Data were less clear for wheat and soy where determining a definitive cut-off was more difficult. We concluded that IgE concentrations to milk, egg, and peanut and, to a lesser extent, wheat and soy, serve as useful predictors of challenge outcome and should be routinely used when advising patients about oral challenges to these foods. See Chapter 15 for additional details on working with your allergist to determine when conditions are relatively safe to proceed with a food challenge to determine if you have outgrown an allergy.
When you eat something and it makes you sick, the logical thing to do is stop eating it. This is essentially what you do with an elimination diet. When you have a food allergy, your doctor often places you on an elimination diet permanently, or until you’ve outgrown the allergy (if you do outgrow the allergy), but doctors often use elimination diets on a temporary basis to diagnose allergies.
You may have already performed this test on your own by avoiding a particular food and then re-introducing it to your diet and finding that your symptoms returned. If you’ve already done this, your doctor should have included this piece of information in your history. If you haven’t performed the test yet, your doctor may recommend it to confirm skin test or RAST results or simply as a logical next step–”we can’t figure this out so let’s avoid certain foods and see what happens.”
An elimination diet typically spans the course of several weeks but consists of only two steps (plus a step that’s sometimes recommended):
Maybe you’re thinking that elimination diet is just a fancy term for food challenge, and it sort of is. You eliminate the food and then challenge it.
Remember: The elimination diet is not foolproof, and it can be risky. Psychological and physical factors can affect the diet’s results. For example, if you think you’re sensitive to a food, a response could occur that may not be a true allergic one. And if you’ve experienced severe reactions to certain foods, your doctor should consider reintroducing the food only in the controlled setting of a food challenge.
Some patients have extremely challenging food allergies that defy the detection efforts of even the most determined and well-trained allergist. To demonstrate just how challenging the diagnostic process can be, I offer a case that typifies the usual patient that I see in my food allergy clinic on a daily basis:
Kyle is a two-and-a-half-year-old old boy who had severe eczema in the first weeks of life. His mother was breast-feeding him at that time, and he seemed to react to whatever his mother was eating. He underwent his first allergy testing at six months of age, and the results showed positive to milk, egg, and peanut. He was weaned to a soy formula, which he appeared to tolerate. By the time he saw me for the first time, he had been skin tested three more times, each test picking up more positive results. A detailed diet history revealed that his only obvious allergic reactions occurred with exposure to egg and milk. He had never ingested peanut or tree nuts and had seemed to tolerate wheat and soy.
Kyle’s previous doctors told his parents that he was truly allergic to all of the foods to which he tested positive. By the time I saw him, his diet was limited to seven foods—rice, apple, pear, chicken, squash, sweet potato, and carrots. Although his eczema was now well under control, he was losing weight and was miserable. The elimination diet had worked to improve his eczema and had been helpful, diagnostically speaking, by showing that his eczema was due to food allergy, but it had truly put him at risk of malnutrition. Given the likelihood that many of his skin test results were falsely positive, I was hopeful that we could expand his diet.
I began by performing RASTs to a large panel of foods. With these results we could put the foods he was avoiding into three categories—almost definitely allergic, possibly allergic, and almost certainly not allergic. I felt that the foods in the last category—almost certainly not allergic—could be safely introduced at home. We were able to quickly expand his diet to include several major foods, including wheat, soy, and corn, as well as many new fruits and vegetables, with no worsening of his eczema. For the foods in the middle category—possibly allergic—I recommended that food challenges be done to further define his true allergies. This allowed us to introduce pork, oat, and potato into his diet. Food challenges to milk and beef were unsuccessful. For the foods in the first category—almost definitely allergic—including egg, peanut, tree nuts, sesame, peas, and fish, I recommended continued strict avoidance.
At this point, while his diet is still very restricted, his life and nutrition are both vastly improved. He will now be retested annually and his diet hopefully will expand further with time.
As described in Chapter 1 and elsewhere, some types of allergy involve other parts of the immune system and are undetectable with the most common allergy tests—skin tests and RASTs. These are mostly gastrointestinal reactions, although occasionally eczema and other rashes may occur due to non-IgE mediated food allergies.
In such cases, allergists typically have to fall back on your history, which may range from tremendously helpful to completely misleading, especially if you experience delayed reactions or you and your doctor can’t pin down a specific food. If the history reveals little useful information, your doctor may recommend one of the following next steps:
Another type of skin testing called patch testing has shown some promise in the diagnosis of non-IgE mediated food allergy. When used for food reactions, small amounts of a pure food are placed in tiny cups, which your doctor tapes to your back. The foods are chosen based on diet, knowledge of common allergens, and previous reactions. Your doctor removes the patches after 48 hours and reads them at 72 hours. During the writing of this book, no standardized reagents, application methods, or guidelines for interpretation are available, and patch testing is still finding its place in the diagnosis of food allergy.
Admittedly, skin tests and RASTs, are less than perfect, but some allergy tests, often purported to be superior, are untested at best, proven to be worthless at their worst, and are usually pretty costly (and not covered by insurance). I commonly see patients who have spent thousands of dollars of these tests and who have been placed on broad avoidance diets based on totally inaccurate test results. Remember those quackologists I talked about earlier in this chapter. They’re typically the misinformed, misguided souls who mislead their patients with these phony tests. Here’s a list of the most common dubious tests to watch out for:
For details about unproven tests and treatments you need to watch out for, skip to Chapter 8.
Certain foods can make you miserable even though you’re not allergic to them. If your doctor examines your body, your history, and your test results and rules out food allergy, he may begin to suspect a food intolerance—an adverse food-induced reaction that does not involve the immune system.
Lactose intolerance is one example of a food intolerance. If you have a lactose intolerance, you lack an enzyme (lactase) that’s essential for digesting milk sugar. In this case, the milk sugar is the culprit. In the case of a milk allergy, a milk protein is the perpetrator. When a person with lactose intolerance consumes milk products, symptoms such as gas, bloating, and abdominal pain may occur. Your doctor can perform a specific test for lactose intolerance called a breath hydrogen test, but for most other food intolerances no specific diagnostic test is available.
To diagnose an intolerance to other foods, such as wheat, your doctor is likely to re-examine the data he’s already collected:
Treatment for a food intolerance is very similar to food allergy treatment. Your doctor is likely to instruct you to avoid the offending foods or at least limit your consumption. The same food substitutes can often help you vary your diet without missing the foods you love. In the case of lactose intolerance, your doctor may prescribe lactase supplements to help you digest the milk sugar.