Food Allergy Epidemic?
If you grew up during the 1960's or 70's, you probably didn't know many people who had a food allergy. Your entire school probably had no more than one or two students with food allergies. Now, the topic is plastered all over the news--in newspapers, magazines, on TV and radio, and across the Internet on websites and blogs like this.
What's going on? Do we have a food allergy epidemic on our hands? What's causing this apparent surge in food allergies?
Although we don't have any rock-solid statistics on the rising prevalence of food allergies, some studies show that over the past 20 years or so, the prevalence of food allergy has risen sharply:
- Reliable evidence gathered over the last 10 years show that the prevalence of peanut allergy has doubled in the last 5-10 years.
- Reliable asthma studies show at least a 100 percent increase in the prevalence of asthma (an allergy-related disease) over the last 30 years. The rise in asthma appears to have preceded the rise in food allergy (which is a source of confusion) although experts believe that similar mechanisms likely underlie the dramatic increases in all allergic diseases.
Anecdotal and clinical evidence (word from the street), strongly support these studies. Doctors are diagnosing more cases, more parents are having to deal with food allergies with their children, and school nurses and pediatricians I have talked to report that they have personally witnessed a significant increase in food allergy cases over the past 10 to 20 years.
So, what's causing this apparent sudden rise in food allergies? No one really knows, but we do have some theories:
- Detection bias: Some people think that the rising prevalence of food allergies is simply due to the fact that doctors are more aware of it and are better able to diagnose it. In other words, food allergies were just as common in the past as they are now, but now we're better at diagnosing them. (Most experts do not hold this view and believe that the increase in food allergies is a very real increase.)
- Hygiene hypothesis: Simply stated, the hygiene hypothesis proposes that the less the immune system is exposed to germs and bacterial by-products, the more energy it has to unleash on allergens. Evidence supporting this theory is that allergies are more common in developed countries and less common in children who grow up on farms, attend daycare in early life, and who have multiple older siblings. Evidence refuting this theory is that some of the highest rates of asthma and allergies are in the inner city where hygiene is often no better than in undeveloped countries.
- Vitamins: We have no clear evidence that vitamin supplements or deficiencies promote the onset of allergies, but a couple small studies have suggested a possible correlation. We just don't know yet.
- Antacids: Theoretically speaking, antacids and other medications designed to reduce stomach acids could have some effect on food allergies, because they affect digestion, but the jury is still out on this one.
- Immunizations or antibiotics: People often blame a host of childhood conditions on the fact that children receive more immunizations and antibiotics now than they did in the past, but we have no reliable evidence to prove that these factors have contributed to the sudden rise in food allergies.
- Tobacco smoke: Of all the studies ever done, the only factor that consistently has been associated with increases in allergy is exposure to tobacco smoke.
Remember: The jump in all allergic diseases across the board suggests that a collection of contributing factors not present 20 or 30 years ago is responsible. Researchers have presented many theories to explain the increase, but the only clear conclusion is that no one, single cause can explain it. I am a doctor and researcher by profession. As such, I am very careful not to jump to conclusions or to take action before all of the facts are in, and I recommend that you take the same, careful approach. Rely on the best medical information and treatment currently available.