Common Questions About Allergies

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Common Questions About Allergies

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Common Questions About Allergies
Common Questions About Allergies
What is an allergy? What causes allergies? These questions and more are answered and explained.
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Reviewed by the Faculty of Harvard Medical School

Common Questions About Allergies

What is an allergy?

An allergy is an exaggerated physical response to an ordinarily harmless substance such as pollen, certain foods or drugs, or to insect stings.

What causes allergies?

Allergies result from a misfiring of the immune system, which normally helps the body to fight off harmful viruses, bacteria and other microorganisms. In an allergic reaction, the immune system behaves as if it perceives pollen, food or other allergens as a threat to health. The immune system defends against the invaders by creating antibodies or producing cell types that set off symptoms every time the allergenic substance enters your body or, in the case of a contact allergic reaction, touches your skin.

Do children outgrow allergies?

Food allergies to milk, wheat, and eggs are usually outgrown. On the other hand, children tend to keep allergies to peanuts, tree nuts, fish and shellfish into adulthood. If children do outgrow allergies it is often by age 3. Until you are advised to do this by a physician, never try out a food that has caused a severe allergic reaction in your child in order to see if the allergy has been outgrown. Allergies other than food allergy may either improve or continue as a child gets older. New allergy triggers may begin to cause symptoms as a child gets older.

Should I move to another part of the country to escape the hay-fever season?

Probably not. You could escape your current hay-fever symptoms by moving to another area, but you also could develop an allergy to a plant native to your new surroundings. If there is a particular season when your allergies are bothersome, it may be ideal for you to choose this time for an out-of-town vacation, however.

Are allergies inherited?

Yes. If one of your parents has a respiratory allergy like hay fever, you have a 30 percent to 50 percent chance of developing allergy symptoms as well. You and your parents may have different triggers. If both your parents have respiratory allergies, there's a 60 percent to 80 percent likelihood that you will also develop allergy symptoms.

Can breastfeeding prevent allergies?

Breastfeeding for at least four months without introducing other foods to your infant is probably the best way to help protect an infant from developing an allergy to cow's milk. However, it is still possible for a baby to develop milk allergy and have symptoms even during the time they are breastfed, because if the mother ingests cow's milk or milk products, small amounts of milk protein can enter the breast milk. Eliminating foods such as milk, peanuts, or egg in the mother's diet during the breastfeeding months has not been proven to noticeably reduce the risk for allergy in children.

What is an anaphylactic reaction?

Anaphylaxis is a severe, life-threatening allergic reaction — usually to foods, drugs or insect venom. The reaction can cause dizziness, throat swelling with blocked breathing, an asthma attack, hives, a sudden drop in blood pressure or unconsciousness. If not treated promptly and correctly, an anaphylactic reaction can be fatal. People who have had one or more episodes of anaphylaxis or severe swelling after an insect sting should carry an emergency kit containing the drug epinephrine for use at the first sign of serious symptoms. Ask your doctor for more information.

Are some animals more likely to cause allergic reactions than others?

Yes. Cats are more likely than dogs to trigger an allergic response. An allergen protein found within the skin and saliva of the animal adheres to animal hair or dander (shed skin). This allergy trigger can enter the air. Loosened hair (coated by allergens) can become airborne and stick to walls and clothing.

How are allergies diagnosed?

Your doctor may be able to diagnose an allergy on the basis of clues from your symptoms and exposures to allergens. For instance, if you have allergy symptoms only during ragweed season, you probably are allergic to ragweed. If you have year-round symptoms, the problem could be dust mites, pet allergies or an allergy to a substance you come into contact with at work. You also may need some tests to identify the allergen. The simplest and most reliable is a skin test that scratches a drop of allergen extract into your skin. If you are allergic to the substance, a reaction usually develops within 15 minutes. A less accurate and more expensive blood test can be used when skin tests aren't practical (if you have eczema or a skin condition that doesn't permit testing) or would be dangerous (if you are severely allergic).

What is the most effective allergy treatment?

Avoiding the substance that causes your allergy. This isn't always possible if you have an allergy to common substances like pollen or dust mites, but you usually can reduce your exposure.


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Last updated July 30, 2014

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