Exposure Time
Most clinics advocate an exposure time of 48 hours (day 2) after application to the patient's back and again at 96 hours(day 4). If late reactions are suspected a third reading could be scheduled on day 7 or 10. Between readings the patient can take a bath but not wash the back.
Removing the Chamber Units
Before removing the chamber units from the patient's back mark the edges with a skin marker (either the regular or the U.V. marker). Some transient erythema may be present after the removal caused by the occlusive effect of the allergens and adhesive.
It is recommended that the first reading be taken 15 to 30 minutes after the chamber units has been removed. This will allow the erythema to settle.
Reading and Interpreting Results
This phase of patch testing is, of course, the most critical...determining the relevance of any reactions to the allergens and their significance to the patient. The result of the reading of each allergen is noted on the Record Sheet (click on "Patch Testing" and "Test Forms" for a copy) using the standard scoring system:
It is suggested that reading of the various Contact Dermatitis reference and resource books can be very helpful in gaining an understanding of this aspect of patch testing. This listing can be found by going to the navigation bar and clicking on "Patch Testing" and clicking on "Reference & Resources".
Once positive reactions are noted and relevance determined advise the patient about sources of exposure, cross reactions, avoidance, etc. It is suggested that the patient be provided with written information specific to their allergies. The dormer.com website provides basic information (click on "Patch Testing" and "Patient Info") that can be added to from other sources.