Patch Test or Skin Allergy Test is a diagnostic method that helps identify the cause of Allergic Contact Dermatitis, which is one of the common skin diseases. Allergic contact dermatitis occurs when the skin comes into direct contact with allergens, causing inflammation, itching, redness at the contact area, and sometimes it may spread widely.
Common Allergens in Daily Life
Contact allergy can be caused by various substances found in cosmetics, skincare products, or everyday chemicals. Common examples include:
- Jewelry and metals such as nickel
- Cosmetics, moisturizers, lipsticks, sunscreens
- Hair dyes
- Rubber and adhesives (plasters)
- Perfumes
- Soaps, shampoos, conditioners
- Fabric softeners
- Toothpaste, deodorants
- Nail polish
- Eye drops
- Steroid creams, topical antibiotics
- Chemicals used in industries or workplaces
- Leather products
Patch Test Procedure
- Apply allergen test patches on the back or upper arm and leave for 2 days
- Visit the doctor 3–4 times according to the testing schedule as follows:
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- Day 1: Apply test substances
- Day 3: Remove patches and read results – 1st reading
- Day 5: Read test results – 2nd reading
- Additional appointment on Day 7 if necessary
Instructions During the Test
- Avoid getting the test area wet
- Avoid exercise to reduce sweating and do not scratch the test area
- Antihistamines can be taken to relieve itching
- Avoid immunosuppressive drugs, oral or injectable, 7–14 days before the test
- Avoid applying steroid creams on the skin areas to be tested (back, upper arm) 1 week before the test
- Avoid sun exposure 1 week before the test
- On the first consultation day, bring suspected products or items with labels and packaging, such as jewelry, cosmetics, etc.
- Testing is not recommended for pregnant or breastfeeding women
Who is it Suitable For?
Patch testing is suitable for individuals with chronic inflammatory skin rashes, especially on the hands, feet, face, and eyelids; recurrent dermatitis of unknown cause or not responding to standard treatment; patients with skin diseases worsened by allergic contact dermatitis; those with chronic skin inflammation and occupations at risk of contact dermatitis such as doctors, dentists, hairdressers, factory workers, construction workers, etc.
This test helps identify the substances causing allergic reactions so patients can avoid them and prevent recurrent skin inflammation, improving the effectiveness of skin disease treatment.
If you have chronic rashes or suspect allergies to cosmetics, skincare products, or everyday chemicals, Patch Testing may be the answer to help restore your skin’s health.
For more information
Dermatology Clinic, Phyathai 1 Hospital
Tel. 02-201-4600 ext. 3325
