Chemical Patch Testing

Chemical Patch Testing

When the skin comes into contact with a substance to which it is allergic or hypersensitive, its reactions can include swelling, redness or blisters, itching, or a burning sensation. Our patients benefit from the expertise of our Allergic Skin Disorders Clinic who can determine the cause of the reaction, which is the first step toward relief.

What is a Patch Test?

A Patch test is a patch testing procedure to diagnose allergic contact dermatitis, whereas the diagnosis of irritant contact dermatitis is based on exclusion of an allergic component. Patch test techniques for diagnosing ACD have been used for over 100 years and the present test methods are based on the established principle of using a testing material (chemical, food etc.) and a delivery device (chamber).

Contact allergen skin testing is a simple and objective scientific method available to our clinic to augment the diagnostic process. Often, the patch test response is the crucial piece of information that allows our clinic 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.

How is The Patch Testing Performed?

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 read after 48 hours. Reactions are read for the second time after 72 – 96 hours 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.

Why 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 specialty skin clinics. 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 specialty skin clinic, accounting for 9.2 million visits in 2004. It also accounts for 95% of all reported occupational skin diseases.