During allergy patch testing, patients must avoid taking medications that can interfere with accurate readings (e.g., antihistamines and some heartburn drugs). They must also take care not to dislodge the test patches from their skin or disturb them in any other way. Allergy patch tests can identify various substances that may trigger contact dermatitis. They can help patients narrow their list of potential allergens and develop a treatment plan accordingly.
What Is Patch Testing?
Allergy patch testing Memphis helps your doctor identify substances that may be causing your allergic skin rash (contact dermatitis). It involves a series of patches containing suspected allergens. These are taped to the back and remain in place for 48 hours (unless they are removed prematurely). Patients should avoid showers or getting the test area wet, excessive sweating, and exercising during this time. Some substances used on the patch test are colored (PPD is black, disperse blue is blue, and textile resins are a variety of colors) to help your allergist see if they are causing a reaction. At your second allergy patch testing appointment, the allergist will lift and evaluate the patches. If a positive reaction is observed, the allergist can then determine whether the substance caused contact dermatitis and will recommend ways to help prevent it in the future. It may include switching beauty products or avoiding certain additives in hair dyes, for example.
What Can Patch Testing Detect?
Allergy patch testing can detect up to 36 different substances that cause allergic contact dermatitis. These include latex, medications, perfumes, hair dyes, and chemicals. Standard allergen series are available, as well as allergy tests tailored to particular occupations and areas of the body, such as dental or hair stylist series. Before your allergy patch test, tell your doctor about any medications or supplements that may interfere with an accurate reading. These can include antihistamines, some antidepressants, and heartburn medicines.
During the patch testing process, your doctor will draw gridlines on your back and apply up to 20 or more adhesive patches that contain various test allergens. These are kept in place with large rectangular pieces of hypoallergenic tape. You will need to leave the patches on for 48 hours, after which your skin will be inspected and the results interpreted. Be careful not to disturb the test sites, and avoid showering until your follow-up appointment two or more days after your allergy patch test.
How Does Patch Testing Work?
Allergy patch testing involves adhesive panels holding small plastic or aluminum chambers filled with different test allergens applied to the clean, dry skin on your back. These are then left on for 48 hours, during which your allergy doctor can watch to see if the patches cause any reactions. If a rash occurs, your dermatologist will use an allergy patch test results chart to discover which allergens might be causing it. Some responses are mild and may be redness, itchiness, or a slight swelling. More severe symptoms include blistering, weeping, or flaking rash. If a standard series of 36 common allergens doesn’t identify the cause, your allergy specialist will apply a set of expanded patch tests to look for chemicals in hair dyes, medications, preservatives, and cosmetics that can cause contact dermatitis. It’s also possible that your allergy doctor will recommend patch testing for substances you come into frequent contact with at work, such as certain chemicals or materials used in floristry, dentistry, and some types of construction.
What Are the Results of Patch Testing?
Allergy patch testing can detect invisible allergens to skin prick and intradermal tests. It can also identify substances that cause contact dermatitis due to your occupation, like the chemicals used in your work environment or certain metals like nickel and gold. Your allergist will recommend the appropriate series of test panels based on your history and symptoms, including specific occupational allergy tests such as a dental or hair stylist series. Each round of testing takes 48 hours to complete and requires you to avoid anything that will dislodge the tapes, such as swimming or excessive exercise. You may experience irritated skin and itching, but this should be clear. Your allergist will then inspect the results and discuss the next steps in your treatment management plan, including avoiding the offending substance medications or changing your home or work environment.