A person may be generally predisposed to have food allergy and be allergic to multiple, unrelated common allergens such as peanut, egg and milk. Or, a person may be allergic to multiple foods only because those foods share similar pro­teins. He emphasizes that being allergic to more than one member of a food “family” varies by the food group, and should bediscussed with your allergist. Sicherer describes a number of relationships among food allergies:

• The peanut allergic have only a 5 per cent chance of reacting to other legumes. The one exception, he says, is the lupin bean. European studies have shown half of people with peanut allergies react to beans from the lupin plant.
• People allergic to one tree nut have a one-in-three chance of allergy to other tree nuts. However, certain nuts tend to pair together, Sicherer says. Cashews and pistachios are similar, walnut and pecan allergies can come together, and almond and hazelnut reactions sometimes go hand in hand.
• Although tree nuts and peanuts are unrelated foods, reacting to both is common. The odds vary by study, but Sicherer says that between one-third to half of peanut-allergic people also have a tree nut allergy.
• A third of the people in the Food Allergy & Anaphylaxis Network’s peanut and tree nut allergy registry also have an allergy to egg. Allergy to chickens’ eggs also increases the likelihood of reacting to other bird eggs, such as quail.
• An allergy to one kind of shellfish puts you at a 75 per cent risk of being allergic to another crustacean.
• It you’re allergic to one type of fish, such as sole, there’s a 50 per cent chance you’ll react to other fish, like cod or bass.
• Allergies to a grain, such as wheat, put you at a 20 per cent risk of reacting to another grain, like barley.
• Twenty two per cent of the nut and peanut allergic people in the FAAN registry are also allergic to milk.
• A person allergic to cow’s milk has a 90 per cent chance of allergy to the milk of most other mammals. About 10 per cent of people who react to milk may also have a problem with beef.
• Allergy to fruit puts a person at a 50 to 90 per cent risk for reacting to other fruits, Sicherer says.

See Also:

• Multiple Food Allergies on the Rise
• Girl with Multiple Allergies: An 11 year-old girl’s story of her multiple, difficult allergies.

The family was waiting on Paige’s appointment with an allergist when 3-year-old Brooke also had a reaction, just days later. “We gave her one peanut, and she immediately dropped to her knees and started vomiting,” Wilson recalls. This was surprising: Brooke had eaten food containing traces of nuts before without incident. Wilson called her doctor back to say, “Now I need a referral for both kids.”

Today at the age of 6, Brooke is allergic to peanuts, and is avoiding all nuts on her allergist’s advice. Paige is allergic to milk, egg, chicken, is avoiding peanuts and tree nuts, and has eczema and several environmental allergies. Michelle and Eldon Wilson always knew their kids could be at risk for food allergies since Eldon is allergic to fish, tree nuts and eggs.

But in that one angst-ridden week, their lives changed forever. After Michelle realized a milk spill “was like a Level 4 biohazard,” the family eliminated allergens from the house. Soy milk became a major source of protein.

Allergists say more and more people like the Wilsons are walking into their offices with longer lists of foods suspected of causing reactions.

“The impression is that there are more people with food allergies, and there are more foods that they’re reactive to,” says Dr. Scott Sicherer, associate professor of pediatrics at the Mount Sinai School of Medicine’s Jaffe Food Allergy Institute. Sicherer, who is the author of Understanding and Managing Your Child’s Food Allergies, also notes that children aren’t outgrowing their food allergies at the same rate they were a few years ago.

In the days before his interview with Allergic Living, Sicherer did a tally of food allergic patients he saw in his New York office. Only three out of 21 were allergic to just one food. Similarly, a 1996 British study of 62 peanut- and tree nut-allergic people found that a quarter of them were allergic to another food, like milk, eggs, sesame or legumes.

But there aren’t many studies yet on the causes of multiple food allergies, as scientists are focused on trying to understand what genetic and environmental factors predispose a person to an individual allergy, like peanut or egg. Sicherer says the population in general is becoming more allergic, including more environmental allergies, eczema and asthma, so more food allergies are just part of that picture.

There is some evidence that multiple food allergies occur in patterns. Some can be explained: for example, someone who is allergic to several types of shellfish.

Other clusters are less obvious. Although peanut is a legume, not a nut, people with tree nut allergies are more likely to have a peanut allergy than the general population, and vice versa. A third of the 5,100 children and adults that the Virginia-based Food Allergy & Anaphylaxis Network has tracked in its tree nut and peanut allergy registry are also allergic to eggs, Sicherer says.

If a baby comes in with milk and egg allergies, “I start to think about peanuts,” Sicherer says. “There’s about a 20 to 25 per cent risk that the child is going to develop a peanut allergy. If that child is not already eating peanuts, I would want to evaluate them for that possibility.”

With the advent of more multiple allergies comes more challenges for allergic people and their families, says Dr. Peter Vadas, director of the division of Allergy and Clinical Immunology at St. Michael’s Hospital in Toronto. Not the least of these can be trying to convince other health professionals how allergic some people are to their grocery list of danger foods.

“I remember patients coming back and telling me their pediatrician was incredulous that the child had so many food allergies,” Vadas says.

Parents, too, can have a hard time grasping a diagnosis of multiple allergies. At first, Karen Eck and her husband Claude Beaucaire of Gatineau, Quebec, didn’t think much about their son Maxime’s troubles with food when he was an infant. Looking back, the boy had warning signs of allergy all along: he threw up frequently, refused to eat some foods, and occasionally got hives.

Eck’s “big wake-up call” was a massive reaction that Maxime had at daycare to green beans just before his second birthday.