Patch Testing for Contact Dermatitis

Serving Hamilton, Stoney Creek, Grimsby and surrounding areas

Where does patch testing take place?
  • Please note that we do not offer patch testing in my office
  • For patch testing I refer patients to:
    • An allergist in the Hamilton area, or
    • The Contact Dermatitis – Patch Test Clinic – St. Michael’s Hospital, Toronto or
    • The Contact Dermatitis – Patch Test Clinic – Sunnybrook Hospital, North York
What is Contact Dermatitis?
  • Contact dermatitis is an inflammatory reaction, or rash, that occurs when substances to which you are allergic come in contact with your skin
  • These substances could be an ingredient in your perfume or aftershave, an antibiotic ointment or cream, rubber boots etc
  • For your Doctor to be testing you with the TRUE Test™ patch, means that he/she is trying to determine what substance you are allergic to

Yes, before patch testing you should:

  • Avoid oral or topical steroids 2 weeks prior to testing
  • Be free from hair, acne, scars, or dermatitis on test area
  • Avoid sun exposure 3 weeks prior to testing
  • Most importantly, make sure that you give your doctor a detailed history of your condition. Let him/her know when it first appeared, all of the areas on your body that are affected, any changes in your use of cosmetic, hygiene, or cleaning products, or changes in your work place, etc.
  • Patch testing is a reliable skin test designed to help your doctor determine whether or not you are allergic to any of the substances included on the test panels
  • The test panels contain twenty-four or more different substances or mixes – all of which are well known causes of contact dermatitis
  • Your doctor will ask you to return when the panel has been on your back for 48 hours
  • At that point the panels will be removed and an initial elevation will be made
  • Should a reaction to any of the substances be present, the reaction could continue to develop over the next 24 to 48 hours
  • Your doctor will determine how long you should wait before your next appointment
  • 1st visit: application of the patches
  • 2nd visit: 48 hours after application your Doctor removes the patches
  • 3rd visit: evaluation within 72 to 96 hours since application
  • Since a reaction to any of the test substances will occur within a certain time period, it is very important that you keep your appointments
  • At each of your next appointments, your doctor will carefully examine the test area for signs of an allergic reaction
  • This reaction usually consists of a rash with swelling, redness and tiny blisters
  • Redness alone, however, does not necessarily mean that you have had an allergic reaction
  • Moisture around the test area must be avoided
  • Therefore, when bathing or showering, you must be careful not to get the test panel or surrounding area wet
  • If the test panel does become wet, it may loosen, allowing the test substances to be washed away
  • For the same reason, any activity such as sunbathing or exercising – which may cause you to sweat or the test panel to loosen should also be avoided
  • If for any reason, an area of the test strip does become loose, you should immediately re-attach it with adhesive tape
  • Try not to scratch the test area
  • If you do, the skin may become irritated and itch even more. Skin that has become red and irritated by scratching will make it difficult for your doctor to interpret the results of the test
  • If you are allergic, your doctor will provide information on where in your everyday surroundings you are likely to come in contact with the offending substances
  • He or she will also tell you how best to avoid these substances and often suggest alternatives to the items that you should avoid