How is a patch test performed?
Unlike prick tests, patch tests do not use needles. Instead, allergens are put onto patches, which are then placed on your skin. Your skin may be exposed to 20 to 30 extracts of substances that can cause contact dermatitis during a patch test. These can include metals, medications, latex, fragrances, hair dyes, preservatives, and resins.
The patch test kit has chemicals that are the offenders in approximately 85–90 percent of contact allergies. This includes chemicals present in foods, drinks, preservatives, metals, rubber, leather, formaldehyde, lanolin, fragrance, toiletries, hair dyes, medicine, pharmaceutical items, and others.
During your first visit, the allergist will apply about 20, or possibly more, substances in small patches taped to the skin of your arm or upper back for 48 hours.
You should not expose the patches to extreme moisture or submerge the patches in water if you bathe. It’s important to allow the allergens to maintain contact with your skin for 48 hours to obtain an accurate reading. Panels that are removed or damaged will require a complete retest.
Is patch testing painful?
Patch testing procedures are simple and painless. To identify specific triggers, your physician will tape several different patches that contain various potential irritants to the skin on the back. These chemicals are then left on the skin for up to 48 hours, and it is crucial that they dry during this time.
It’s important to remember that there are a near limitless number of patch tests that can be performed. Standard tests include 20 or more items. A negative test to one patch test does not necessarily mean that you do not have contact dermatitis. What this means is that you are not sensitized to any of the reagents tested. If all of the patches in the initial test are negative, additional tests may be recommended based on your history.
How long does a patch test take?
Positive patch test results are determined when a reaction of dermatitis appears on the affected area. The affected areas will be itchy and might require treatment with a topical steroid. Sometimes patch test reactions can persist for several weeks.
Patch tests take two visits to your doctor. The duration of the test is typically 48 hours, to eliminate any chances of a delayed reaction to the allergen.
However you choose to test, you normally need to wait at least 24 hours to see the side effects of a patch test – and in some cases, it’ll be 48 hours. After the allocated period of time, you’ll need to check for any signs of redness, itchiness or swelling.
During the 48 hours the patches are on your skin, your doctor will most likely advise you to avoid getting any moisture on the patches, this includes showering and doing things that cause heavy sweating. After you go back to the doctor, they will remove the patches and conduct a thorough investigation on the areas in question to see if you’ve had a reaction.
If you or someone you know are experiencing symptoms of allergies or are unsure of the cause of your allergic reactions, please contact our office for more information on patch testing in the South Miami, FL area. To book an appointment with Piniella Asthma and Allergy call us at (305) 515-5922 or visit us online at www.pa2allergy.com. We are located at 6705 SW 57th Ave, Ste 520 South Miami, FL 33143.