More than 50 million people in the United States have allergies. If you often have allergy symptoms – such as itchy, watery eyes; a runny nose; wheezing; and hives or itchy skin – an allergy test can help determine what you’re allergic to.
Finding out what allergens trigger your body’s defenses is an important first step in effective allergy treatment. Tests help identify allergies to pollen, molds, dust mites, animal dander, insect stings, foods, and some medicines.
A small amount of a suspected allergen is scratched, or “pricked,” on the skin's surface, usually the back or a forearm. Sometimes the allergen may be injected into the skin on the arm. If you have an allergy, slight swelling or redness will occur. Skin tests must be performed in a doctor’s office to minimize risks of severe reactions.
Allergy blood tests may be an option for patients when skin tests might be unsafe or won’t work, such as if certain medications are prescribed; if there is a skin condition (eczema or psoriasis) that may interfere with skin testing; or if the patient is a baby or small child unable to tolerate numerous skin pricks.
The patch test is typically performed to see if a patient has a delayed reaction to an allergen, usually a food. A small amount of the suspected allergen is placed in an aluminum chamber, in contact with the skin for 48 hours. Areas of the skin that become inflamed indicate a delayed allergic reaction.