Patch Test
Introduction
Skin tests are used by doctors to determine which substance you are
allergic to. The test exposes your skin to an allergy-causing substance
(allergen) and the doctor then observes to see if there is an allergic reaction.
A “patch test” is a skin test in which the allergen is applied to a patch worn
by the patient for a period of time. It is convenient, safe and painless, and an
excellent test for determining the cause of contact dermatitis, a skin problem
caused by allergic reactions to items that you touch.
Preparation for the Test
- Before the test your doctor will discuss your medical history and
perform a physical examination .
- Your doctor will need a list of any medications you might be taking as
they can interfere with the test results.
- Stop the use of topical steroids on the back for at least a week prior
to the test.
- Take a clear bath before the test, as the patch will remain on the back
for 72 hours.
During the Test
- Take care not to disturb the patch and be careful not to wet the area
where the patch is placed.
- Avoid strenuous activities that lead to perspiration.
- Lie and sleep on your side or front to avoid disturbing the patch.
- The test may cause an itchy allergic reaction. If the itchiness is
unbearable, return to the hospital for removal of the part causing the
itchiness.
Reading the Results
- After 48 hours, your doctor will remove the patch and “read” the
results. Some marks might be placed on your back with a marking pen. Take
care not to wet this area, as it will disturb the marks.
- After 72 hours, you will return to the doctor for a second reading of
the results.
- In some instances, patients have a slow reaction that doesn’t appear
until after 72 hours. Be sure to inform your doctor if a reaction develops
after the last reading.
Side Effects
- Itchy patches caused by a reaction to the allergen.
- A dark mark left from the test that will disappear in a short time.
For more information, please contact
Bangkok Skin & A Center
Tel. (662) 310 3004, (662) 755 1004
Email : info@bangkokhospital.com