Q. I have long wondered: Is eczema directly linked to cow’s milk allergy?
Dr. Sicherer: The allergic form of eczema, also known as atopic dermatitis, is related to other allergic illnesses including asthma, allergic rhinitis (hay fever) and food allergies. These illnesses are inherited and often occur together in the same person.
Infants and children who are known to be allergic to milk are more likely to have atopic dermatitis and other allergies. Infants with atopic dermatitis are more likely to have positive allergy tests to milk as well as other food and environmental allergens such as dust mite and cat dander.
Milk allergy is not necessarily directly linked with the eczema, but both are more likely to occur in allergy-prone individuals.
The more severe the allergic skin rash and the earlier the onset, the greater the chance that the infant may have, or develop, other allergies, including food allergies. Again, this probably reflects a person’s general allergic inclination, rather than being a direct link between a food and the skin rash.
But could there be a direct link between allergy and eczema? One theory is that the broken, rashy skin allows proteins to be “seen” by the immune system, while normal skin keeps out the allergens. This might make it easier for the immune system to attack the proteins that land on the broken skin, causing more allergies. However, this is just a theory.
One direct link between milk allergy and eczema is when the ingestion of milk actually triggers the rash.
Although milk is sometimes a trigger, there are many common triggers, including skin infection, irritants, the itch-scratch-itch cycle and various allergens in the environment.
Removing milk from the diet as a form of treatment carries nutritional and social risks, so dietary changes should only be done with medical supervision. If medical treatment for atopic dermatitis fails to provide relief, the possibility that milk (or other foods) is a trigger can be explored with an allergist.
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, Associate Chief of the Division of Allergy and Immunology at Children’s National Medical Center in Washington, 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.