Allergy Testing: How to Prepare & What to Except.

This September, 4C Medical Group will begin allergy testing in our Scottsdale clinic.

Do you have symptoms such as skin rashes, bellyaches, headaches, lethargy, and/or difficulty breathing?  You may be suffering from an allergic reaction.

Your doctor will give you a physical examination and ask detailed questions about your familial and personal health history to determine if your symptoms are caused by an allergy. Before your allergy test, it is vital you disclose all medications you are taking; certain medications interfere with the accuracy of the tests and may cause severe reactions to the allergen extracts.

Here is a list of medications that are known to interfere with testing (via Mayo Clinic):

  • Prescription antihistamines,such as levocetirizine (Xyzal) and desloratadine (Clarinex).
  • Over-the-counter antihistamines, such as loratadine (Claritin, Alavert), diphenhydramine (Benadryl, others), chlorpheniramine (Chlor-Trimeton), cetirizine (Zyrtec, others), and fexofenadine (Allegra).
  • Tricyclic antidepressants, such as nortriptyline (Pamelor) and desipramine (Norpramin).
  • Certain heartburn medications, such as cimetidine (Tagamet) and ranitidine (Zantac).
  • Asthma medication omalizumab (Xolair).This medication can disrupt test results for six months or longer even after you quit using it (most medications affect results for days to weeks).

Once the medications clear your system (up to 10 days) you’re ready for testing. Here’s what to expect:

Allergy testing is performed by a nurse in your doctor’s office. The process takes 20 to 40 minutes. Some allergy tests cause immediate allergic reactions (within minutes), while others develop results over several days dig this.

There are three types of allergy tests:

Skin Prick Test

This non-invasive test, also known as the puncture or scratch test causes immediate allergic reactions. 40 substances are tested simultaneously (i.e., pollen, mold, pet dander, dust mites and food).

Adults are tested on their forearms, while children are tested on their upper backs. Rest assured, skin prick tests are not painful and minimally penetrate the skin using a needle, only scratching the surface of the derma. The nurse will begin by cleaning the test site with alcohol, marking the skin, and applying a drop of allergen next to each mark. He or she will prick the skin, allowing the allergen extract to seep in. Next, two additional substances will be applied: histamine (most people are reactive to this substance) and glycerin or saline (most people are non-reactive to these substances). Within 15 minutes, the nurse will inspect the test sites to determine if wheals (raised red, itchy bumps mimicking mosquito bites) develop. He or she will record the results (to be reviewed by your doctor) and remove the test marks using alcohol.

Skin Injection Test 

This test offers immediate in-office results. A small amount of allergen extract is injected under the surface of the skin (on the arm). Within 15 minutes, a reaction will develop if an allergy is present.

Skin Patch Test

Allergens are applied to patches adhered directly to the skin (of the arm or back) to determine if specific substances are causing skin irritation (contact dermatitis). 20 to 30 extracts are tested during the skin patch test including irritants such as latex, medications, fragrances, preservatives, hair dyes, metals, and resins.

The patches are applied in the office and worn for 48 hours. It is important to avoid bathing or sweating until they are removed. After the 48 hours, the patches are removed to determine if dermatitis is present.

It is important to note that false positives and negatives do occur during skin testing due to environmental and physiological influences. Retesting may be necessary. If you do test positive, you and your doctor will create an allergy treatment plan which includes changes to your environment and diet, prescription medications, and immunotherapy to keep you symptom-free.

Read the full article here.


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