An allergy is an overreaction, or hypersensitivity, of the body’s immune system. Normally, your immune system works to fight off foreign substances like viruses and bacteria. When you have an allergy, your immune system treats a harmless substance, like dust, pollen, or even food, as a threat. To fight this perceived threat, your immune system reacts and causes an allergic reaction. Symptoms of an allergic reaction can range from sneezing and a stuffy nose to a life-threatening condition known as anaphylactic shock. So, how can you figure out what substances you’re allergic to?

There are two main types of allergy tests: blood tests and skin tests. The type of test used to diagnose an allergy may depend on the type of suspected allergy.

Allergy blood test measures the amounts and levels of IgE antibodies in the blood. A small amount of IgE antibodies is normal. A larger amount of IgE may mean you have an allergy.

Allergy skin test usually checks for allergies caused by Type 1 hypersensitivity, which includes dust mites, pollens, foods, animal dander, and medicines such as penicillin. Skin tests look for reactions to allergens placed directly on the skin or just below the skin surface.