Scratch Testing Information
Patient Instruction/Consent Form for Allergy Skin Testing
Skin Test: Skin tests are methods of testing for allergic antibodies. A test consists of introducing small amounts of the suspected substance, or allergen, into the skin and noting the development of a positive reaction (which consists of a wheal, swelling, or flare in the surrounding area of redness). The results are read at 15 to 20 minutes after the application of the allergen. The skin test methods are:
Prick Method: The skin is pricked with a plastic needle where a drop of allergen has already been placed.
Intradermal Method: This method consists of injecting small amounts of an allergen into the superficial layers of the skin. Intradermal tests have a higher risk of adverse allergic reactions and, as such, are not performed at GI for Kids.
Interpreting the clinical significance of skin tests requires skillful correlation of the test results with the patient’s clinical history. Positive tests indicate the presence of allergic antibodies and are not necessarily correlated with clinical symptoms.
You will be tested to foods, including dairy, soy, wheat, peanuts, fish, shellfish, and eggs among others. The skin testing generally takes 30 to 45 minutes. Prick (also known as percutaneous) tests are usually performed on your back but may also be performed on your arms. If you have a specific allergic sensitivity to one of the allergens, a red, raised, itchy bump (caused by histamine release into the skin) will appear on your skin within 15 to 20 minutes. These positive reactions will gradually disappear over a period of 30 to 60 minutes, and, typically, no treatment is necessary for this itchiness. Occasionally local swelling at a test site will begin 4 to 8 hours after the skin tests are applied, particularly at sites of intradermal testing. These reactions are not serious and will disappear over the next week or so. They should be measured and reported to your physician at your next visit.
1. No prescription or over the counter oral antihistamines should be used 5 days prior to scheduled skin testing. These include cold tablets, sinus tablets, hay fever medications, or oral treatments for itchy skin, over the counter allergy medications, such as Claritin (loratadine), Zyrtec (cetirizine), Allegra (fexofenadine), Benedryl (diphenhydramine), Periactin (cyproheptadine) and many others. If you have any questions whether or not you are using an antihistamine, please ask the nurse or the doctor. In some instances a longer period of time off these medications may be necessary.
2. Nasal and eye antihistamine medications should be stopped 2 days prior to your scheduled skin testing. These include Patanase, Pataday, Astepro, Optivar, and Astelin. In some instances a longer period of time off these medications may be necessary. If you have any questions whether or not you are using an antihistamine, please ask the nurse or the doctor.
3. Oral H2 blockers, including Zantac (ranitidine), Pepcid (famotidine), Axid (nizatidine), and Tagamet (cimetidine), should be stopped 2 days prior to your scheduled skin testing. Proton pump inhibitors such as Prevacid (lansoprazole), Prilosec (omeprazole), Protonix (pantoprazole), and Nexium (esomeprazole) do not need to be stopped for the skin testing.
4. Medications such as over the counter sleeping medications (e.g. Tylenol PM) and other prescribed drugs, such as amytriptyline hydrochloride (Elavil), hydroxyzine (Atarax), doxepin (Sinequan), and imipramine (Tofranil) have antihistaminic activity and should be discontinued at least 2 weeks prior to receiving skin test after consultation with your physician. Please make the doctor or nurse aware of the fact that you are taking these medications so that you may be advised as to how long prior to testing you should stop taking them.
5. No oral corticosteroids, including Prednisone and Prednisolone, should be used 5 days prior to scheduled skin testing. Inhaled corticosteroids, including inhaled and swallowed Flovent, do not need to be stopped for the skin testing.
6. If you are taking any of the above medications for chronic medical conditions and you have concerns about stopping the medications for any period of time, please contact the prescribing doctor’s office for further information.
1. You may continue to use your intranasal allergy sprays such as Flonase Rhinocort, Nasonex, Nasacort. Omnaris, Veramyst and Nasarel.
2. Asthma inhalers (inhaled steroids and bronchodilators), leukotriene antagonist s (e.g. Singulair, Accolate) and oral theophylline (Theo-Dur, T-Phyl, Uniphyl, Theo-24, etc.) do not interfere with skin testing and should be used as prescribed.
3. Most drugs do not interfere with skin testing but make certain that your physician and nurse know about every drug you are taking (bring a list if necessary).