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What is an Allergy?

An allergy is a hyperactive immune response by an individual to substances called allergens which include dust, pollen, fungi, animal fur, insect venom, specific foods or certain medications that are usually harmless to most people. The reactivity towards an allergen is often caused by genetic factors and varies from one person to another.

Symptoms of Allergies

The onset of symptoms after exposure to an allergen may be immediate or delayed by several hours to several days depending on the type of allergen, the site of exposure and the response of the individual. The common symptoms of an allergic reaction are:

  • Skin Rashes
  • Cough and shortness of breath
  • Wheezing
  • Fever and headache
  • Nausea and Vomiting
  • Sneezing and Coughing
  • Fatigue

Types of Allergic Conditions

The various types of allergic conditions that can be diagnosed by skin and blood allergy tests include:

  • Allergic asthma
  • Food allergy
  • Antibiotics allergy (penicillin)
  • Latex allergy caused by rubber gloves
  • Dermatitis (Skin allergy)
  • Hay fever
  • Bee venom allergy
  • Seasonal allergy

How do Skin and Blood Allergy Tests work?

During a skin allergy test, your skin is exposed to allergens and you may develop an allergic reaction such as itching and a red bump. A blood allergy test is performed to detect an increase in specific antibodies (proteins) in your blood called Immunoglobulin E (IgE) on exposure to an allergen. Excess IgE causes the release of histamine that is associated with allergy symptoms.

Preparation before the Test

Your doctor will discuss your history of allergic reactions. You may be advised to avoid certain foods or medications that may interfere with the test.

Procedure for Skin and Blood Allergy Testing

Skin Allergy Test

  • Skin Injection: The allergen is injected into your skin and the injection site is observed for allergic reactions after about 15 minutes.
  • Skin Prick Test: Your healthcare provider applies a small amount of allergen to your skin. A lancet is used to prick your skin and the site is observed for immediate allergic symptoms.
  • Patch test: A patch containing the allergen is placed on your skin, usually on your arm or back. The results are tested after 48 hours. It is an important test to detect contact dermatitis.


  • Safe and can be performed on children and adults
  • Fast and inexpensive
  • Can be used to test allergens such as dust, insect venom, pollen, and certain drugs
  • More than one allergen can be tested at once

Blood Allergy Test

  • A small amount of blood is drawn with the help of a needle and syringe
  • The concentration of IgE in the blood is measured
  • An elevated concentration indicates an allergy


A blood allergy test may be preferred if you are on medication that could interfere with skin allergy testing results, cannot tolerate multiple needle pricks to your skin, or have a history of an extreme allergic reaction to allergens.

Alexandria Medical Associates

Primary care

6355 Walker Lane,
Suite 303,
Alexandria, VA 22310

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