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Allergy Tests

How It Is Done continued...

The health professional drawing your blood will:

  • Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.
  • Clean the needle site with alcohol.
  • Put the needle into the vein. More than one needle stick may be needed.
  • Attach a tube to the needle to fill it with blood.
  • Remove the band from your arm when enough blood is collected.
  • Apply a gauze pad or cotton ball over the needle site as the needle is removed.
  • Apply pressure to the site and then a bandage.

The blood sample will be placed on specially treated paper and sent to a lab to determine whether antibodies to any of the allergens being tested are present. If specific antibodies are found, it may mean you are allergic to a certain allergen.

How It Feels

Skin tests

With the skin prick test and the intradermal skin test, you may feel a slight pricking sensation when the skin beneath each sample is pricked or when the needle penetrates your skin.

If you have an allergic reaction from any of the skin tests, you may have some itching, tenderness, and swelling where the allergen solutions were placed on the skin. After the testing is done, cool cloths or a nonprescription steroid cream can be used to relieve the itching and swelling.

If you are having a skin patch test and you have severe itching or pain under any of the patches, remove the patches and call your doctor.

Blood test

You may feel nothing at all from the needle puncture, or you may feel a brief sting or pinch as the needle goes through the skin. Some people feel a stinging pain while the needle is in the vein. But many people do not feel any pain or have only minor discomfort after the needle is positioned in the vein.

Risks

Skin tests

The major risk with the skin prick test or the intradermal skin test is a severe allergic reaction called anaphylaxis. Symptoms of a severe allergic reaction include itching, wheezing, swelling of the face or entire body, trouble breathing, and low blood pressure that can lead to shock. An anaphylactic reaction can be life-threatening and is a medical emergency. Emergency care is always needed for an anaphylactic reaction. But severe allergic reaction is rare, especially with the skin prick test.

If you are having a skin patch test and you have severe itching or pain under any of the patches, remove the patches and call your doctor.

Blood test

There is very little risk of a problem from having blood drawn from a vein.

  • You may develop a small bruise at the puncture site. You can reduce the risk of bruising by keeping pressure on the site for several minutes after the needle is withdrawn.
  • In rare cases, the vein may become inflamed after the blood sample is taken. This condition is called phlebitis and is usually treated with a warm compress applied several times daily.
  • Continued bleeding can be a problem for people with bleeding disorders. Aspirin, warfarin (Coumadin), and other blood-thinning medicines can also make bleeding more likely. If you have bleeding or clotting problems, or if you take blood-thinning medicine, tell your doctor before your blood is drawn.

WebMD Medical Reference from Healthwise

Last Updated: June 30, 2011
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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