According to the American Academy of Allergy, Asthma, and Immunology, AAAAI, 40 to 50 million individuals in the U.S. population suffer from at least one allergen. In order to diagnose and treat allergy symptoms, a physician that specializes in allergy and immunology will perform a common procedure known as allergy skin testing. During allergy skin testing, small amounts of various allergens are indented--or pricked--under the skin surface to determine a positive or negative diagnosis. To ensure the validity of skin test results, certain medications should be avoided.
Antihistamines
Antihistamines are medications that prevent the onset of allergy symptoms by suppressing the production of histamine released in the body. The desired outcome of allergy skin testing is to activate an allergic response that will determine the causative allergen. Over-the-counter or prescribed medications that contain antihistamines, such as diphenhydramine, Benadryl and loratadine, Claritin, can hinder results and people should avoid taking them for a minimum of 48 to 72 hours prior to testing.
H2 Blockers
Similar to antihistamines, H2 blockers alter the production of histamine levels in the body. However, they differ from antihistamines in that they block histamine receptors in the stomach rather than the skin and nose. Many over-the-counter as well as prescribed acid reflux medications contain H2 blockers such as famotidine, Pepcid and ranitidine, Zantac. A study conducted by the American College of Allergy, Asthma and Immunology, ACAAI concluded that H2 blockers do not significantly interfere with allergy testing. Nevertheless, accepted protocol still recommends the avoidance of these medications at least 48 to 72 hours before allergy testing.
Tricyclic Antidepressants
Contrary to the H2 blocker study findings, the ACAAI discovered that over half of patients taking Tricyclic antidepressants, TCA failed to respond to skin testing. Examples of medications categorized as TCA's include amitriptyline, Elavil and doxepin, Aponal. Although the exact reason has yet to be determined as to why TCA's conflict with histamine levels, they should still be discontinued under the advice of a healthcare provider 48 to 72 hours preceding testing.
References
- American Academy of Allergy, Asthma, and Immunology (AAAAI): Allergy Statistics
- American Academy of Allergy, Asthma, and Immunology (AAAAI): Allergy Skin Testing
- American College of Allergy, Asthma & Immunology (ACAAI) 2009 Annual Scientific Meeting: Abstract 23. Presented Nov. 8, 2009
