It’s hard to eat something that looks tasty, like a pumpkin muffin or a brownie, in front of children, without them asking for a bite. I coach a bunch of energetic 7-10 year old swimmers at the local YMCA, and at our meets, I have access to the hospitality table of snacks for coaches and officials. Every time I try to eat something, I am swarmed by my athletes, asking if I can share a bite of a muffin, or get them some crackers. I have taken to telling them that I have a “Don’t Feed the Children” rule, just like when you go to the zoo, there is a “Don’t Feed the Animals” sign. I explain that I don’t know if they have any food allergies, and if I fed them something that made them sick, I’d feel pretty bad. So, if they are hungry, they have to go see their official keepers (aka mom and dad) to provide safe snacks.
I’m not sharing this simply to demonstrate my convenient excuse for not sharing my much-need muffin with my swimmers. Food allergies, ranging from digestive intolerance to full anaphylactic shock, seem to be on the rise in this country. A 2008 CDC study showed an 18 percent increase in food allergies in U.S. kids between 1997 and 2007. Researchers have documented the rate of peanut allergies doubling, as reported by parents. The question remains; are food allergies actually increasing significantly or are we just doing a better job of testing kids for sensitivity?
Allergies occur when the immune system decides to attack something foreign, like pollen or dust or peanuts. The immune system’s fight is what creates the symptoms, because the allergen is not, in itself, dangerous to human health. Severe food allergies can be fatal, with more than half of the fatal incidents of anaphylactic shock due to peanuts. The most common allergens are milk, egg, peanut, tree nuts, shellfish, fish, wheat, and soy. In 2011, researchers at Duke published the largest survey of childhood allergies to date, sampling 40,000 random households. They found that eight percent of children have food allergies, and three percent had severe allergies. A full two percent reported peanut allergies.
The science on food allergies is complex and often contradictory. Peanuts make a great example, because it scares people that this common component of the childhood diet could cause severe reactions. There appears to be a genetic component, as kids with siblings with peanut allergies are also likely to have peanut allergies. The allergic reaction is also linked to peanut exposure, both positively and negatively. Maternal consumption of peanuts was linked to allergies, and before 2008, mothers were warned not to eat peanuts while pregnant, but in 2008, new evidence indicated that scientists actually still don’t know how in-utero exposure to peanuts affects allergies. The American Association of Pediatrics reacted its previous position, and now states that we don’t know enough to recommend for or against maternal consumption of peanuts.
Here’s an illustration from Journal of Allergy and Clinical Immunology, from a 2007 article on Peanut Allergies by Sicherer and Sampson, considering all of the factors that might contribute to the peanut allergy:
What is it about peanuts?
Why are peanuts, in particular, such a serious allergen? Peanuts are legumes, more closely related to beans then they are related to other nuts. The reason that people with peanut allergies are told to avoid tree nuts is that they are frequently processed on the same equipment, leading to contamination, not because the nuts share similar properties.
Peanut allergies are more common in the U.S. and the U.K., where people tend to eat peanuts roasted, than in Asian countries like China, where peanuts are usually eaten raw or boiled. Studies have shown that the allergic response to one of the peanut proteins, Ara h 2, is increased by the roasting process.
The primary treatment for peanut allergies is to avoid peanuts. Which, in children, is often harder than in sounds, leading to schools banning all peanut products to prevent kids from switching sandwiches and such. In about 20 percent of young children with peanut allergies, the allergy fades away as they age. In trials of oral immunotherapy, where subjects with peanut allergies are repeatedly exposed to very small amounts of peanuts, significant desensitization occurred for most patients. It has yet to be shown that these effects remain after the treatment stops. There have been a few incidents of allergic reactions, although not severe, during these treatments.
Allergy Development Hypotheses
Studies have suggested that perhaps the fear of peanut allergies, leading parents to avoid feeding young children peanuts, has in fact lead to more peanut allergies. A 2008 study comparing Jewish children in Israel to Jewish kids in the UK, found that the British babies had ten times the rate of peanut allergy, compared to the Israeli babies. The Israeli children consumed 7 grams on peanuts on average, per month, between 8-14 months of age, and the British children had no peanut exposure at that age. The theory is that the babies developed tolerance to peanuts through early exposure, rather than developing an allergic reaction when the first exposure occurs in an older child.
Lots of other hypotheses abound for allergies, beyond early and maternal exposure. They are described in Lack’s 2008 report on Epidemiological Risks In Food Allergies. One is that a shift in consumption of dietary fats from animal fats to vegetable fats has lower omega-3 fatty acids and increased omega-6 acids, which alters production of lymphocytes involved in immune system response. This theory has also been linked to asthma and eczema, but there is little evidence.
Vitamin D has been shown to play a role in immune system, that could relate to allergic response. A study looking at EpiPen prescriptions (to treat/prevent anaphylaxis from allergies) found more than twice as many prescriptions in the Northern U.S. states than in the Southern states, which have considerable more exposure to sunlight, producing more natural vitamin D. However, more research is definitely needed on this hypothesis as well.
A longer standing theory, known as the hygiene hypothesis, suggests that in our clean, modern lifestyle, we are not exposed to enough microbes to keep our highly evolved and effective immune systems busy. This leads the immune system to over-react to insignificant things, and cause allergies. Studies have developed supporting data for this theory, but no particularly strong evidence in food allergies has been shown. However, you can listen to a guy who gave himself hookworms to keep his immune system busy, so that it would stop giving him debilitating allergies, here on Radiolab.
So, what do I conclude about the peanut allergy? It’s really complicated and there is lots of interesting research trying to figure out why rates are increasing, how we can treat it, and what mechanisms in the body actually contribute in a meaningful way to our immune system’s sometimes misguided responses. Food allergies are field of research to watch, and a solid reason not to feed peanut butter chocolate chip cookies to stray children!
Gupta et al. “The Prevalence, Severity, and Distribution of Childhood Food Allergy in the United States” PEDIATRICS Vol. 128 No. 1 July 1, 2011 pp. e9 -e17
Varshney et al. “A randomized controlled study of peanut oral immunotherapy: Clinical desensitization and modulation of the allergic response” Journal of Allergy and Clinical Immunology Volume 127, Issue 3, March 2011, Pages 654-660