Dermatologists apply patch tests in patients with dermatitis, to find out whether their skin condition may be caused or aggravated by a contact allergy. Patch tests are not the same as skin prick tests, which are used to diagnose hay fever allergy (house dust mite, grass pollens and cat dander). Skin prick tests have very limited value for patients with skin rashes.
Dr. Groysman received extensive training in allergy testing. She was selected to become a member of American Contact Dermatitis Society and has access to extensive allergy database that only a few doctors have.
A range of substances can be used for patch testing. North American test patch series are applied to nearly every patient, together with specific tests appropriate to the individual. Each substance (known as an allergen) has been tested to find the best concentration to demonstrate an allergic reaction without causing irritation to those who are not allergic to the material.
The first appointment will take about half an hour. Tiny quantities of 70 materials in individual square plastic or round aluminium chambers are applied to the upper back. They are kept in place with special hypoallergenic adhesive tape. The patches stay in place undisturbed for 72 hours. You may take antihistamines during the 72 hrs, but not oral steroids. You will return at 72 hrs to get patch test reading.
At the second appointment, usually three days later, the patches will be removed. The back is marked with an indelible black felt tip pen or other suitable marker to identify the test sites.
We will complete a record form at 72hrs. The result for each test site is recorded. The system we use is as follows:
- Negative (–)
- Irritant reaction (IR)
- Equivocal / uncertain (+/–)
- Weak positive (+)
- Strong positive (++)
- Extreme reaction (+++)
Irritant reactions include sweat rash, follicular pustules and burn–like reactions. Uncertain reactions refer to a pink area under the test chamber. Weak positives are slightly elevated pink or red plaques. Strong positives are ‘papulovesicles’ and extreme reactions are blisters or ulcers. The relevance depends on the site and type of dermatitis and the specific allergen. The interpretation of the results requires considerable experience and training.
You will be given a printout of the allergens that you are allergic to. You will also be emailed a product list of all products that you can use on regular basis.