Allergy Patch Test: How Contact Allergy Is Checked

Who it may help

People with suspected contact dermatitis, unexplained facial or hand rashes, or reactions to cosmetics, metals or workplace substances may be advised to test.

The schedule

Allergens are applied, usually on the back, and left in place for a set period. Return visits are needed for readings. You may be asked to avoid wetting the area and heavy sweating.

Not every rash has an identifiable allergen. Results, when they are positive, guide avoidance rather than offering a one-time cure.