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 perceives pollen, food or other allergens as a threat to health. The immune system defends against the invaders by creating antibodies 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 can be 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. Other allergy symptoms may improve as a child gets older, but new ones may develop.
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 could develop an allergy to a plant native to your new surroundings. Moving usually is not a practical solution to a pollen allergy.
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 one, though not necessarily the same allergy. If both your parents have respiratory allergies, there’s a 60 percent to 80 percent likelihood that you will also develop an allergy.
Can breast-feeding prevent allergies?
There’s no proof that breastfeeding protects the children of allergic parents from developing allergies at some point later in life, but it could delay the onset of the allergies. Delaying the introduction of solid foods can further prolong the allergy-free period in babies who inherit a tendency toward allergy.
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, breathing problems, 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 at risk for these reactions should carry an emergency kit containing the drug epinephrine for use at the first sign of 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 attaches to animal hair or dander (shed skin) when the pet grooms itself. Loosened hair 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 your symptoms and exposure 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 will develop 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.
Revision date: July 8, 2011
Last revised: by Janet A. Staessen, MD, PhD