During allergy skin tests, your skin is exposed to suspected allergy-causing substances (allergens) and is then observed for signs of an allergic reaction. Along with your medical history, allergy tests may be able to confirm whether a particular substance you touch, breathe or eat is causing symptoms.

Why it's done

Information from allergy tests may help your doctor develop an allergy treatment plan that includes allergen avoidance, medications or allergy shots (immunotherapy).

Allergy skin tests are widely used to help diagnose allergic conditions, including:

• Hay fever (allergic rhinitis)
• Allergic asthma
• Dermatitis (eczema)
• Food allergies
• Penicillin allergy
• Bee venom allergy

Skin tests are generally safe for adults and children of all ages, including infants. In certain circumstances, though, skin tests aren't recommended. Your doctor may advise against skin testing if you:

• Have ever had a severe allergic reaction. You may be so sensitive to certain substances that even the tiny amounts used in skin tests could trigger a life-threatening reaction (anaphylaxis).
• Take medications that could interfere with test results. These include antihistamines, many antidepressants and some heartburn medications. Your doctor may determine that it's better for you to continue taking these medications than to temporarily discontinue them in preparation for a skin test.
• Have certain skin conditions. If severe eczema or psoriasis affects large areas of skin on your arms and back — the usual testing sites — there may not be enough clear, uninvolved skin to do an effective test. Other skin conditions, such as dermatographism, can cause unreliable test results.

Blood tests (in vitro immunoglobulin E antibody tests) can be useful for those who shouldn't or can't undergo skin tests. Blood tests aren't used for penicillin allergy.

In general, allergy skin tests are reliable for diagnosing allergies to airborne substances, such as pollen, pet dander and dust mites. Skin testing may help diagnose food allergies. But because food allergies can be complex, you may need additional tests or procedures.

Having an allergy increasers your risk of certain other medical problem including :Anaphlaxis. Its for severe allregies symptoms.
Keep your home and car clean of pollen: On days when pollen counts are high, keep your doors and windows closed. Stay inside, especially during afternoons and evenings when pollen levels are highest. Cool your home using air conditioning but stay away from humidifiers and swamp coolers.

You may need an allergy blood test if you have:

• Allergic rhinitis (hay fever), usually the result of pollen, pet allergies or mold (aspergillosis).
• Anaphylaxis, which is a severe and sometimes life-threatening allergic reaction to certain foods, insect stings or other allergens.
• Contact dermatitis, caused by contact with irritants such as chemicals, detergents, poisonous plants or certain metals (such as a nickel allergy).

Allergy symptoms may include:

• Abdominal pain.
• Cough.
• Diarrhea.
• Dry skin.
• Eczema.
• Headache.
• Hives (urticaria) and swelling (angioedema).
• Itchy, red or watery eyes.
• Nausea and vomiting.
• Shortness of breath (dyspnea).
• Skin rash.
• Sneezing.
• Sore throat (pharyngitis).
• Stuffy, itchy or runny nose.
• Swollen lips, tongue, eyes or face.
• Wheezing, tightness in your chest or allergic asthma.

Test Result interpretaion.

An allergy blood test checks for antibodies called immunoglobulin E (IgE) in your blood. Antibodies are proteins your immune system produced in response to harmful substances such as viruses or bacteria. If you have an allergy, your body produces IgE in response to the allergen even if it’s harmless.

Common allergens include:

• Certain foods or ingredients.
• Dust.
• Latex.
• Insect bites and stings.
• Mold.
• Pet dander.
• Pollen.
• Some medications.

They used to call this type of allergy test a radioallergosorbent test (RAST) because it used radioactivity, but now it no longer uses radioactivity.