Your Genes - Why Are You Allergic: Allergies

Content provided by the Faculty of the Harvard Medical School

Your genes

While many people suffer from allergies, others don’t. If you’re one of the unlucky ones, blame your parents. Scientists now know that many people have a genetic predisposition to be allergic. For instance, a child with one parent who has allergies has a 50% risk of developing allergies. And this risk increases to 70% if both the child’s parents are allergy sufferers.

Someone with a genetic predisposition to allergies is said to be atopic , and more likely to suffer from childhood atopic dermatitis (eczema), atopic rhinitis, and atopic asthma. Atopic allergies typically first appear in very young children with the signature itchy, red rash of eczema. These children may go on to develop the sneezing, runny nose, and congestion of atopic rhinitis (sinus symptoms) around year one or two. And many then go on to develop atopic asthma (lung symptoms) by age five or six. Unfortunately, unlike early allergies to certain foods, there’s little likelihood of outgrowing these particular allergies. Consequently, people who are atopic are typically afflicted with more than one type of allergy throughout their lives. Atopic diseases are often referred to as allergic diseases.

What’s in a name? Allergy and atopy are not synonymous. Allergy describes an individual’s hypersensitivity to an allergen upon a second or subsequent exposure after an uneventful initial exposure, meaning you’ll get away with it the first time but not the second. Atopy means you are genetically predisposed to be allergic to certain allergens from the start. People who are atopic have a predisposition to allergic reactions. But keep in mind, a predisposition isn’t an automatic sentence. You may be one of the lucky ones who has a genetic predisposition, but — for whatever reason — doesn’t go on to develop allergies. The reverse is also true: You may not be genetically predisposed, yet develop allergies anyway.

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Last updated:	August 21, 2006
Reviewed By:	Faculty of Harvard Medical School

Medical content reviewed by the Faculty of the Harvard Medical School. Harvard Health Publications, Copyright © 2007 by President and Fellows of Harvard College. All rights reserved. Used with permission of StayWell.

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