. Last Updated: 07/27/2016

Allergy's Hit List: Milk, Eggs, Peanuts

A pastry. A sandwich. A hamburger roll. A piece of chocolate. A bowl of soup. A ladle full of gravy. Simple, seemingly safe foods, yet to children and adults with food allergies, they are potentially lethal.


One of the hardest things about having a food allergy is convincing people that it is real. Food allergies "are still not taken seriously by the vast majority of people, including the vast majority of physicians,'' said Robert Wood, director of the pediatric allergy clinics at Johns Hopkins Medical Institutions in Baltimore, who has his own allergy to peanuts.


For people who are allergic to peanuts, milk, eggs, almonds, walnuts, pecans, soy, wheat, fish or shellfish, eating a meal can be like trying to walk through a minefield.


Food allergies occur in genetically susceptible individuals, usually those who have a family history of asthma, hay fever and eczema. Most food allergies surface early in life, usually by about the third birthday.


"Milk and egg allergies are the number one and two food allergies'' in youngsters, Wood said. "Peanuts and soy are next.'' Allergies to tree nuts, such as almonds, pecans and walnuts, then fish, shellfish and wheat follow.


By age 3, however, 85 percent of children who are allergic to milk and eggs outgrow their allergy, leaving peanut allergy the leading problem for older children and adults.


Why youngsters overcome their reaction to milk and eggs is not understood. "We think that their immune system is maturing and becoming more tolerant,'' said Sampson. "One of the big challenges is to figure out what has happened that enables them to now drink milk.''


If researchers could understand those changes, they might be able to prompt the immune system to stop overreacting to peanuts and shellfish, the two most stubborn food allergies and the type that very few seem to outgrow.


One theory is that the proteins found in peanuts and shellfish (the substances that the immune system reacts to in a food-allergy attack) are particularly stable. "They're not usually affected by enzymes in the saliva and acids in the stomach,'' said Mayo Clinic allergist John Yunginger. "They're also more resistant to cooking, baking and roasting,'' which normally break down proteins and make them less likely to produce an allergic reaction.


Once people encounter a food to which they are allergic, their immune systems are primed to overreact the next time they eat the food. This leads to a rapid reaction.


A New England Journal of Medicine study, published in 1992 by Sampson and his colleagues, found that some food-allergy symptoms can begin as quickly as one minute after exposure. Among the most common are rashes, hives, nausea, vomiting, cramping, diarrhea, itchy palms and soles of the feet as well as swollen lips, nasal congestion, coughing, hoarseness and a runny nose.


But certain foods are such potent irritants of an allergic person's immune system that they can cause an anaphylactic reaction. Blood pressure plummets, breathing stops and death ensues unless steps are taken immediately.


Doctors recommend that patients carry both oral antihistamines and a small, pen-like device that carries epinephrine, a form of adrenaline that helps stop the symptoms. The device enables patients to give themselves a quick injection in the thigh when an attack occurs.


One of the most powerful irritants is the common peanut -- and it is increasingly present in food. Peanut butter-and-jelly sandwiches are a favorite in many American homes, akin to Mom and apple pie.


Peanut flour is also showing up as a filler in a wide variety of foods including chili, spaghetti sauce, split-pea soup and gravy. Cold-pressed, unrefined peanut oils are increasingly used in cooking.


Even supposedly peanut-free candies, cookies and baked goods can have a peanut residue when they are prepared with the same baking pans or utensils.


For a small but growing percentage of young children, peanuts pose a serious risk.


Estimates are that 5 percent of children under age 6 are allergic to peanuts, making it one of the leading food allergies in youngsters. But unlike many other food allergies that can cause hives, nausea or swelling, peanuts can create a much more severe reaction in allergic people, sometimes leading to death.


What worries experts is that the incidence of peanut allergy appears to be increasing in the United States. Allergist Hugh Sampson and his colleagues at Johns Hopkins tested two groups of children treated at the same allergy clinic a decade apart and found that the number of youngsters allergic to peanuts doubled from 1984 to 1994.


Allergists throughout the country report treating more children with peanut allergy, suggesting that the rate of peanut allergy "certainly would appear to be going up,'' Sampson said.


Even peanut growers are concerned. "Our industry first became aware of the issue a few years ago and began working internally to make sure that all manufacturing members were labeling products and to make sure that cross contact didn't occur,'' said Kim Cutchins, president of the National Peanut Council in Alexandria, Va.


Why peanut allergies are increasing is not understood, although some experts believe it may be linked to earlier exposure to peanuts. Doctors believe that some problems can be avoided if foods known to cause allergies are not given to children in allergy-prone families until the immune system has a chance to mature, usually between ages 2 and 3.


Because peanut butter and peanut products are so common in children's diets, however, that can be difficult. A study by Kaiser-Permanente pediatric allergist Robert Zeiger in San Diego found that about 80 percent of infants had received some peanut butter by their second birthday even in families where doctors had advised waiting until age 3 to introduce the food.


"The other thing is that a lot of mothers tend to eat peanut butter when they are breast-feeding, and we know that foreign food proteins are transmitted in breast milk,'' Sampson said. "We don't know what role that might play.''


"In general, it has been recommended that children under age 3 not have peanuts introduced into their diets,'' said Brett Kettelhut, chairman of the Adverse Reactions to Food Committee of the American Academy of Allergy, Asthma and Immunology.


Some groups are taking even stronger measures. Two schools in North Andover, Mass., asked all parents to keep peanut products out of children's lunches and snacks after school officials learned that six students had peanut allergies.


As Kathleen Callagy, principal of one of the schools, said in an interview with The Boston Globe, "We are trying to do everything we can to limit the risk to these children, because from what we understand, the threat is real and very scary.''