According to the American College of Allergy, Asthma & Immunology, more than 50 million people suffer from allergies. Allergies can be bothersome and manifest as sneezing, itchy eyes and runny nose. Some allergies, such as allergies to foods or to insect stings, can even be life-threatening and result in rashes, vomiting and difficulty breathing. The first step in effective treatment of allergies is diagnosing the specific allergens that affect a patient.
Background
An allergist is a physician who has had training in medicine or pediatrics and then advanced training in allergic disease. After listening to how the patient is affected by an allergy, the allergist determines whether allergy testing is needed. In some cases, the patient's story leads the allergist to believe that the symptoms causing the patient trouble aren't related to an allergy, and thus testing won't benefit the patient. In many cases, the physician decides whether the patient should be tested with a skin test or with a blood test. Allergy testing can be used to diagnose allergies to things in the environment, foods, certain medications and insects.
Types
The two main types of testing for allergens are skin testing and blood tests. In order to undergo skin testing, a patient must avoid taking antihistamines and other medications that interfere with the results. Patients with skin disease such as atopic dermatitis may have difficulty undergoing skin testing because the severity of the rash can interfere with the results. For patients who cannot undergo skin testing, blood tests can be performed that look for evidence of an immune response against specific allergens.
Procedures
During a skin test procedure, a small amount of the allergen is placed on a thin piece of plastic. This is then used to lightly scratch the skin. These scratches are usually placed on the forearm or on the back. After 20 minutes, the allergist examines the areas that have been scratched and measures the reaction. In a positive reaction, the skin becomes red and swollen at the site of the scratch. Multiple allergens are often tested simultaneously; the tests are done on the back or the forearm. The blood test involves a needle stick and the collection of tubes of blood for analysis. Skin testing results are available immediately after testing; blood tests results take one or two weeks.
Risks
The biggest risk of skin testing is itching and redness at the site of a positive reaction. In rare cases, a patient with severe allergies may develop a systemic response that requires treatment by a physician. The itching typically resolves in a few hours. For blood testing, the risk is similar to that of any blood draw and involves bleeding and pain at the site of the needle stick.
Benefits
Once a patient knows what he is allergic to, a treatment plan that reduces the symptoms of allergies can be devised. This may involve avoiding a potential allergen, medications and even vaccinations against certain allergens. The treatment depends on the specific allergy of the patient and the symptoms the patient has associated with the allergy.
