What is Patch Testing?
Patch testing has been a tried-and-true diagnostic tool used by dermatologists for decades. If you are suffering from allergy-induced skin rashes without knowing the irritant, patch testing can provide the answers to get you the treatment you need.
Patch testing attempts to reproduce the allergic reaction on the normal skin on the upper back of the patient. The patches are applied and subsequently removed after 48 hours. Reactions are read after 72 – 96 hours and often, again at 7 days after removal. The diagnostic value of patch testing depends upon the choice of test substance, the vehicle, the concentration, results interpretation and patient counseling. Patch tests are comprised of materials that occur in the home, work and/or recreational environment.
Patch Testing for Proper Diagnosis of Contact Dermatitis
Appropriate diagnosis and management of persistent eczematous conditions such as contact dermatitis are common challenges for the dermatologist when patch testing. In 2008, the prevalence of contact dermatitis in the general U.S. population was variably estimated between 1.5% and 5.4% and reported to be the third most common reason for patients to seek consultation with a dermatologist, accounting for 9.2 million visits in 2004. It also accounts for 95% of all reported occupational skin diseases.
Contact allergen skin testing is a simple and objective scientific method available to physicians to augment the diagnostic process. Often, the patch test response is the crucial piece of information that allows for the early identification of the offending allergen(s) and confirmation of a diagnosis of Allergic Contact Dermatitis (ACD) and/or Irritant Contact Dermatitis (ICD). Once a diagnosis is achieved, the patient can then take appropriate action to avoid exposure to the allergen and, if possible, substitute non-allergenic agents.
What to Expect from Patch Testing
Patch testing typically involves three exams that are typically scheduled over the course of four days. During this time it is advised that patients avoid exposing the test site to water or sun, which means patients should forgo showering over the course of treatment. Sponge baths are allowed for areas, which are not taped, such as armpits or lower body. For the first appointment patients are advised to bring along items that their skin is exposed to on a daily basis (lotions, cosmetics, plants, medication, or clothing) to be used in the testing process. Patients should wear loose-fitting clothing that is easily removed, such as a button-down shirt, to avoid interfering with the patches’ placement. Patients should also temporarily avoid strenuous exercise, which would cause them to sweat or move around too much, potentially loosening the patches. During an initial consultation, the dermatologist will also be able to let you know whether certain medications you take might interfere with the testing.
Overall, patch testing is an efficient and pain-free tool for diagnosing one’s specific allergy or set of allergies. Upon discovering your triggers, Dr. Ghatan will offer guidance on how to avoid contact with the offending allergens and provide the appropriate treatment.
If you are experiencing skin rashes that may be a result of allergic contact dermatitis, contact our office today.
