Precautions You Need to Take Before Allergy Skin Test

Your doctor will ask detailed medical history, signs and symptoms of your current medical problem (for which you want to undergo allergy skin test). Your answer may be useful information for your doctor and help in finding the possible causative agent (allergen) that may be causing problem for you. Certain allergies may run in families and your doctor may determine that based on your history. Additionally your doctor may do physical examination.

Your doctor will also ask in detail about the medications and supplements you may be taking at present. It is therefore important you bring all the medications you are currently taking, both prescription medications as well as over the counter medications. Many medications can suppress allergic reaction and may interfere with the result of allergy skin test. And there are certain medications that may cause severe allergic reaction during allergy skin test and may give false positive result. Your doctor may ask you to bring the list of all medication you have taken in last 10 days, because different drugs take varying time to clear from your system. The following medications can interfere with allergy skin test:

  • Antihistamines: both prescription antihistamines (levocetirizine, desloratadine etc.) and over the counter antihistamines (diphenhydramine available as Benadryl, fexofenadine available as Allegra, pheniramine, cetirizine etc.) interfere with allergy skin test result.
  • Heart burn medications such as ranitidine (Zantac), cimetidine (Tagamet)
  • Tricyclic antidepressants such as nortryptaline, desipramine etc.
  • Certain anti-asthma drugs such as omalizumab. This medication can interfere allergy skin test results for 6 months or more after taking the last dose and your doctor may ask specifically about this medication.

Result of your allergy skin test:

The allergy skin test result by skin prick test and intradermal injection will be known before you live your doctor’s office. However, for patch test it may take a few days to get the final result as the result is delayed by at least 48 hours.

A positive allergy skin test result indicate that you may be allergic to a particular substance. The bigger the measurement of wheal, the greater is the risk of allergy. If you have negative result, i.e. no wheal, it indicate that you probably do not have allergy.

However, it is important to keep in mind that the results are not always accurate. There can be false positive (you do not have allergy to any substance, but the result is positive) and false negative (you have allergy to a substance, but the result is negative) allergy skin test results. In fact, same person may react differently to same test on two different occasions.

Depending on your allergy skin test result your doctor will plan modalities for treating your allergy problem. Treatment modalities include, use of medications, immune therapy, change of dietary habits, change of home, change of working environment such as change of a job. With proper planning it is possible to keep allergy at bay.

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