Venom skin testing is the most sensitive form of venom testing and continues to be the benchmark used by most allergists. A large number of allergy cells or mast cells reside in the skin providing a very accessible area to diagnose venom allergies. An alternative to venom skin testing is the blood test (RAST), which has a lower sensitivity but it is very useful in patients who have had severe stinging insect reactions and may not be able to tolerate skin testing.
A nurse will prick the forearm with an applicator containing a small amount of venom. Positive reactions on skin testing are typically a red, itchy area with a raised center that may look like a mosquito bite. Skin testing on the back is compared with negative (saline) and positive (histamine) control tests to help gauge the intensity of the reaction. If necessary, the doctor may also recommend an additional intradermal skin test.
Medications & Allergy Testing
The following medications may interfere with allergy testing and should be discontinued prior to the test procedure:
1. Antihistamines. Patients should not use many over-the-counter antihistamines, cold medications and sleeping aids such as Benadryl (diphenhydramine), Chlor-Trimeton (chlorpheniramine), Tavist (clemastine), Robitussin Night Time andTylenol PM at least three days prior to the testing.
Additionally, patients should not use over-the-counter Claritin or Alavert (loratadine), Allegra (fexofenadine) along with Zyrtec (cetirizine) one week prior to skin testing.
Prescription antihistamines, such as Xyzal (levocetirizine) and Clarinex should also be stopped seven days prior to the skin testing. Astelin, Astepro and Patanase nasal spray should be stopped five to seven days prior to testing, but intranasal steroids may be continued.
2. Beta-blockers. Patients should not use beta-blockers when testing is planned. These drugs must not be discontinued without physician guidance, so it is extremely important to consult the allergist to design a discontinuation program if skin testing is required.
3. Antidepressants. Patients should discontinue the use of some antidepressants such as amitriptyline one week prior to skin testing. However, some of the newer antidepressant-type medications do not interfere. Please contact the office with the names of your medications to find out which antidepressants might interfere with allergy testing.
Please call the office for any questions on medications.