Allergy Skin Testing

Allergy skin testing is done to find out allergy to inhalants (pollens, dust, pets, molds), foods, insect venoms (e.g. honey bee), Penicillin. 


The procedure involves putting drop of the antigen (allergen to be tested) over the skin of the forearm or back and breaking the skin barrier with prick or scratch.  This helps the antigen being tested to come in contact with immune cells in the skin layer.  These cells are called mast cells and they contain histamine.  When allergic person comes in contact with allergens, mast cells release the histamine in the area.  This shows up as a red itchy welt over the skin. 


The tests are read about 15 minutes after testing is done.

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Medications to Avoid:

Medications can interfere with results
Before scheduling a skin test, bring your doctor a list of all of your prescription and over-the-counter medications. Some medications can suppress allergic reactions, preventing the skin testing from giving accurate results. Other medications may increase your risk of developing a severe allergic reaction during a test.

Because medications clear out of your system at different rates, your doctor may ask that you stop taking certain medications for up to 10 days.

Medications that can interfere with skin tests include:

  • Prescription antihistamines, such as fexofenadine (Allegra) and desloratadine (Clarinex).

  • Over-the-counter antihistamines, such as brompheniramine (Dimetapp), loratidine (Claritin, Alavert), diphenhydramine (Benadryl, others), chlorpheniramine (Chlor-Trimeton), cetirizine (Zyrtec, others), doxylamine (Vicks NyQuil, Alka-Seltzer Plus).

  • Tricyclic antidepressants, such as amitriptyline and doxepin.

  • Certain heartburn medications, such as cimetidine (Tagamet) and ranitidine (Zantac).

  • The asthma medication omalizumab (Xolair). This medication can disrupt test results for six months or longer even after you quit using it (most medications affect results for days to weeks).