Allergies Explained

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Allergic reactions are inappropriate, overblown responses mounted by the body’s immune system against a harmless substance — take ragweed pollen, for example. Ragweed pollen is not poisonous, infectious, or in any way harmful to humans. But in some people it triggers an attack by immune system cells that takes the form of an allergic reaction. When this happens, the ragweed pollen — or any offending substance — is called an allergen. You develop allergies for two reasons: First, you are genetically predisposed to be allergic; second, factors in your environment, especially when you are young, make you more susceptible. Most allergies are caused by some combination of genetics and environment. 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 (see What’s in a Name?), 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. Do you suffer from any of these?