woman blowing her nose into a tissue Share on Pinterest
LaylaBird/Getty Images

We include products we think are useful for our readers. If you buy through links on this page, we may earn a small commission.Here’s our process.

Your immune system is responsible for defending the body against bacteria and viruses. In some cases, your immune system will defend against substances that typically don’t pose a threat to the human body. Some of these substances are known as allergens, and when your body reacts to them, it causes an allergic reaction.

You can have an allergic reaction after inhaling, eating, or touching an allergen. Doctors can also use allergens to diagnose allergies and can even inject them into your body asa form of treatment.

The American College of Allergy, Asthma & Immunology (ACAAI) reports thatover 50 million peoplein the United States have some type of allergy.

Doctors don’t know why some people experience allergies. Allergies appear to run in families, which means they can be inherited. If you have a close family member who has allergies, you’re at greater risk for developing them.

The reasons why allergies develop are unclear, but some substances are known to commonly cause an allergic reaction. People who have allergies are typically allergic to one or more of the following:

过敏反应的症状可能会有所不同mild to severe. If you become exposed to an allergen for the first time, your symptoms may be mild. These symptoms may get worse if you repeatedly come into contact with the allergen.

Mild reaction

Symptoms of a mild allergic reaction can include:

Severe reaction

Severe allergic reactions(usually to foods, insect stings, and medications) can cause the following symptoms:

A severe and sudden allergic reaction known asanaphylaxiscan develop just seconds after exposure to an allergen. This type of reaction results in life threatening symptoms, including:

If you experience anaphylaxis, seekimmediate emergency help. Without treatment, anaphylaxis can result in death.

Aprimary care physicianor anallergistcan diagnose allergic reactions.

If you experience symptoms of an allergic reaction, the doctor will perform an exam and ask you about your health history. If your allergic reactions are severe, they may ask you to keep a journal that details your symptoms and the substances that appear to cause them.

The doctor may want to order tests to determine what’s causing your allergy. The most commonly ordered types ofallergy testsare:

  • skin tests
  • challenge (elimination-type) tests
  • blood tests

Skin test

A skin test involves applying a small amount of a suspected allergen to the skin and watching for a reaction. The substance may be:

  • taped to the skin (patch test)
  • applied via a small prick to the skin (skin prick test)
  • injected just under the skin (intradermal test)

A skin test is most valuable for diagnosing:

Challenge (elimination-type) test

Challenge testing is useful in diagnosing food allergies. It involvesremoving a food from your dietfor several weeks and carefully watching for symptoms when you eat the food again.

Blood test

Ablood test让医生检查your blood forantibodiesagainst a possible allergen. An antibody is a protein your body produces to fight harmful substances.

Blood tests are an option when skin testing isn’t helpful or possible.

If you experience an allergic reaction and you don’t know what’s causing it, you may need to see a doctor to determine which substances you’re allergic to. If you have a known allergy and experience symptoms, you may not need to seek medical care if your symptoms are mild.

In most cases,over-the-counter antihistamines, such as diphenhydramine (Benadryl), can be effective in controlling mild allergic reactions.

Shop for over-the-counter antihistamines online.

Treatment for anaphylaxis

If you or someone you know experiences a severe allergic reaction, you should seek emergency medical attention. Check to see if the person is breathing, call 911 or your local emergency services, and provideCPRif needed.

People with known allergies often have emergency medications with them, such as an epinephrine auto-injector (EpiPen, Adrenaclick, Auvi-Q). Epinephrine is deemed a “rescue drug” because it opens the airways and raises blood pressure.

The person may need your help to administer the medication. If the person is unconscious, follow these steps to help prevent shock:

  1. lay them on their side
  2. elevate their legs
  3. cover them with a blanket

Once you identify what’s causing your allergic reaction, you can take the following steps:

  • avoid exposure to the allergen
  • seek medical care if you’re exposed to the allergen
  • carry medications to help treat anaphylaxis

You may not be able to avoid an allergic reaction completely, but these steps can help you prevent future allergic reactions.

If you have a known allergy, preventing an allergic reaction will improve your outlook. You can do this by avoiding your allergens whenever possible.

Your outlook will also depend on the severity of your allergy.

If you have a mild allergic reaction and seek treatment, you’ll have a good chance for recovery. However, symptoms may return if you come into contact with the allergen again.

If you have a severe allergic reaction, your outlook will depend on receiving quick emergency care, since anaphylaxis can result in death. If you have severe allergies, always carry an epinephrine auto-injector and inject yourself if symptoms occur.

Prompt medical care is also necessary to improve your outcome.