Q: I have two young children, and my 18-month-old daughter has had an anaphylactic reaction to dairy.
I’ve been letting her older brother continue to eat cheese at lunch, but sometimes he’ll touch or grab his sister’s arm before I can wash him up. This happened recently and she got a few hives. Could skin exposure worsen her allergy? Should we just give up on cheese?
Dr. Sicherer: From a practical and quality-of-life point of view, most families do not ban common allergens (such as milk, egg, soy or wheat) from the home. Rather, they educate themselves on how to ensure the allergic child doesn’t end up ingesting the allergen.
That said, the age of the child is a consideration. An 18-month-old is more likely to grab and eat another child’s food or put contaminated items in her mouth, which is a risk for a severe reaction. Risk also increases when the non-allergic child is too young to understand why he should not share his food with his allergic sibling.
But these risks can be managed. For example, a family meal might include the allergen, while snacks eaten by the children unsupervised by the television exclude it.
The larger question is whether skin or other casual exposure to foods might promote or worsen allergy. One study suggests that higher levels of home exposure  to peanut may increase the risk of developing a peanut allergy. This observation matches the knowledge that allergies to cats or pollens, for example, are related to environmental exposure. However, living with a cat to which there is allergy may not necessarily “worsen” the allergy.
To complicate the picture further, there is a study that suggests that the skin may be a route for immunotherapy – a potential treatment for food allergy that is under study. While studies have not adequately addressed the theoretical concern about these types of exposures, it is reassuring that most young children outgrow allergies to many foods that are common in the home, such as egg, milk, wheat and soy.
Most experts would likely agree that for a food such as milk, the theoretical concerns of promoting the allergy through skin contact should be balanced against practical and quality of life issues for the entire family.
Work with your allergist to review the risks and to rationally address ways in which your family can enjoy food while ensuring safety for your allergic child.
Dr. Scott Sicherer is Chief of the Division of Allergy and Immunology of the Jaffe Food Allergy Institute  at the Icahn School of Medicine at Mount Sinai in New York. Together with Dr. Hemant Sharma, he writes “The Food Allergy Experts” column in the American Edition of Allergic Living magazine. Questions submitted below will be considered for answer in the magazine.