Auckland Allergy & Eczema Clinic

Patch Testing – Patient Instruction Sheet

Patch Testing – Patient Instruction Sheet

We believe that your skin disease may be related to contact with chemicals in your environment. This is called allergic contact dermatitis.

The only way to obtain proof of allergic contact dermatitis is by patch testing. This is different from skin prick testing (which gives a positive response in 15 minutes) in that it is a delayed hypersensitivity response (positive response in about 48 hours).

Chemicals will be taped to your back in small chambers. The skin will not be broken. The "patches" stay in place for 48 hours. You cannot shower or do any work or exercise that will wet or loosen the patches.
The "patches" will be removed, and a reading will be done after 2 days. The patch sites will be marked, and you may be asked to return for a final reading on another day. Between the two readings you can bathe, but you may not wash your back.

You may develop itching under the patches. If it becomes very severe or if you develop pain, you should contact the clinic. If you are unable to contact the clinic, have someone carefully remove the painful patch. Try not to disturb the other patches.

You may develop blisters at the positive sites, and very rarely prolonged reactions or even scars may develop at such sites.

You will be tested for your response to common chemicals. If you believe that any agent or product even a medication worsen your problem, please bring it with you (and the container with the ingredient list) when you come for patch testing.

You should not be tested if you are taking cortisone pills (eg. prednisone), have had a cortisone injection, are applying cortisone to your back, or have had sun on your back recently. Please tell the nurse or doctor if any of these have occurred. Please tell the doctor if you are pregnant. Please call if you have any problems. Please ask if you have any questions.

Your tests may be completely negative. This probably means that a contact allergy is not the cause of your skin problem. The test is not infallible, however, and an allergy may be missed. Retesting in the future may be indicated.

Allergens tested in the Standard Patch Test

  • Potassium Dichromate
  • Neomycin Sulphate
  • Thiuram mix
  • Paraphenylendiamine
  • Cobalt Chloride
  • Benzocaine
  • Formaldehyde
  • Colophony
  • Clioquinol
  • Balsam of Peru
  • N-Isopropyl-N-Phenyl parapheylendiamine
  • Wool alcohols- Lanolin
  • Mercapto mix
  • Epoxy resin
  • Paraben mix
  • Partertiarybutyl-Phenol Formaldehyde Resin
  • Fragrance mix
  • Quaternium
  • Nickel Sulphate
  • 5-chloro-2-methyl-4-isothiazolin
  • Mercaptobenzothiazole
  • Sesquiterpene lactone mix
  • Primin
  • Alpha-amyl-chinnamaldehyde
  • Compositae Mix