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    Mayo Clinic Q and A: Number of children with peanut allergies has increased significantly

DEAR MAYO CLINIC: Why is it that so many kids these days have peanut allergies? I don’t remember it being an issue even 20 years ago. Is it something most kids will grow out of? I have heard of children doing a peanut allergy study to “cure” them of their allergy. What does that involve?

food allergies sign that says 'no peanuts' next to peanut butter jarANSWER: You’re correct that the number of children with peanut allergies has increased significantly over the last several decades. Although researchers have several theories, at this time there’s no definitive explanation for the increase. A variety of studies are currently underway to better understand peanut allergies and to help find more effective ways of treating them.

Over the last several decades, the prevalence of peanut allergies in children in the United States has more than tripled. The reasons behind this dramatic increase are unclear. Lifestyle, diet choices and genetics all seem to play a role.

For example, one theory, called the hygiene hypothesis, highlights how the way people who live in developed countries may have an impact on childhood allergies, including peanut allergies. Babies born in developing countries have lower incidence of allergies than those in developed countries. But if a family moves to a more developed country, their children’s incidence of childhood allergies increases. So simply being in the environment of a developed country seems to change things.

The hygiene hypothesis suggests that children who have more exposure to germs and certain infections at a very early age develop immune systems that are better suited to differentiating harmless substances from harmful substances. In this theory, exposure to certain germs teaches the immune system not to overreact. It would also explain why children who grow up on farms or those who have certain types of pets are less likely to develop allergies than other children. But much more research is needed to understand exactly how childhood germ exposure might help prevent allergies.

In about 20 percent of people who develop a peanut allergy when they are young, the allergy eventually goes away over time. The remaining 80 percent have some sensitivity to peanuts throughout their lives, although the severity of symptoms varies widely from one person to another.

Of note, peanuts are actually legumes and not related to other nuts, known as tree nuts. Unfortunately, many children with peanut allergy go on to develop tree nut allergy. In addition, tree nuts can be cross-contaminated or confused with peanuts, so for these reasons, we often ask children with peanut allergy to avoid tree nuts as well.

A variety of research studies are looking at possible ways to treat peanut allergies. A number of them involve giving a small amount of peanut protein to children with peanut allergies, and then increasing the amount over time. In some of these studies, children eat the peanut proteins, while in others a patch on the skin is used to deliver them. The goal is to make children less sensitive to peanuts so if they have a small exposure, it won’t result in anaphylaxis — a potentially life-threatening allergic reaction that causes blood pressure to drop and airways to narrow and restrict breathing.

There has been some success with these studies. They do come with risks, however. In addition to the possibility of anaphylaxis, some participants in these studies have developed a condition called eosinophilic esophagitis. It is the result of certain white blood cells called eosinophils building up in the lining of the esophagus, damaging the esophageal tissue and making it hard to swallow. Because of these risks, children in these studies need to be carefully monitored.

At this time, the most effective way to manage a peanut allergy is to strictly avoid peanuts and to always carry an injectable dose of the medication epinephrine to use for emergency treatment in the event of accidental peanut exposure.

If you have a child who is allergic to peanuts, or you suspect a peanut allergy in your infant or toddler, consult with a pediatric allergist. These specialists can provide a thorough evaluation and offer comprehensive education on how to best deal with a peanut allergy. Martha Hartz, M.D., Pediatric Allergy and Immunology , Mayo Clinic, Rochester, Minn.