Allergy Intradermal Skin Testing

Praana Center for Asthma and Allergy

What is intradermal allergy skin testing?

Intradermal skin testing is a diagnostic test used to help determine whether you or your child is allergic to specific environmental allergens. This test is sometimes recommended when additional information is needed beyond standard skin prick testing.

I may recommend intradermal skin testing as part of a comprehensive allergy evaluation to better understand your symptoms and guide an effective treatment plan.

How do you prepare for the test?

Proper preparation is essential for accurate results. Antihistamines and certain other medications can interfere with skin testing and must be stopped ahead of time. Please review the instructions below carefully and check with me before stopping any prescription medications.

If antihistamines are not stopped as directed, we may not be able to complete your testing.

Stop the following oral antihistamines 5 days before your appointment:

  • Allegra® (fexofenadine)

  • Atarax®, Vistaril® (hydroxyzine)

  • Zyrtec® (cetirizine)

Stop the following oral medications 3–4 days before your appointment:

  • Actifed®, Dimetapp® (brompheniramine)

  • Benadryl® (diphenhydramine)

  • Chlor-Trimeton® (chlorpheniramine)

  • Claritin® (loratadine)

  • Clarinex® (desloratadine)

  • Phenergan® (promethazine)

  • Tavist®, Antihist® (clemastine)

  • Combination cold/allergy medications such as Actifed®, Aller-Chlor®, Bromfed®, Drixoral®, Dura-Tab®, Novafed-A®, Ornade®, Poly-Histine-D®, and Trinalin®

  • Zyflo® (zileuton)

  • Acid-reducing medications including Tagamet® (cimetidine), Zantac® (ranitidine), Pepcid® (famotidine), and Axid® (nizatidine)

If you are taking an oral antihistamine not listed here, please stop it 3–5 days before your appointment. Many over-the-counter cold and flu products contain antihistamines, so read labels carefully (for example, Tylenol® Allergy or Tylenol® Cold & Flu).

Stop the night before your appointment:

  • Singulair® (montelukast)

  • Accolate® (zafirlukast)

Some antidepressants, sleep aids, and nighttime pain medications (such as Tylenol® PM, Advil® PM, and NyQuil™) may also affect test results. Please let our office know if you take these medications. Do not stop them without first speaking with the prescribing physician.

Additional preparation instructions:

  • Stop all supplements 3 days before testing (discuss with your provider if you have concerns)

  • Do not apply lotions or creams to your back or forearms on the day of testing

  • Continue all other medications as prescribed unless instructed otherwise

What happens during intradermal skin testing?

During intradermal skin testing, a very small amount of each suspected allergen is injected just under the surface of the skin, usually on the back or arm.

If you are allergic to a substance, a small raised bump with redness will develop at that site. After a short period of time, we carefully measure each reaction for size and redness.

A sufficiently large reaction suggests sensitivity to that allergen. I then interpret your test results in the context of your symptoms and medical history to determine whether a true allergy is present.

How long does the test take?

Intradermal skin testing typically takes 30–40 minutes to complete.

What should I expect on the day of my test?

Please arrive 15–20 minutes before your scheduled appointment to allow time for check-in. Our team will guide you through the process and ensure you are comfortable throughout the visit.

If you have any questions before your appointment, please contact our office.