Marking patch tests sites: description of a practical, clean, durable and inexpensive method

We propose an original method to mark patch test sites. A transparency is applied on the patient's back, surrounding patch tests, immediately after their application. Marks are performed with an erasable pen on test sites and on permanent skin lesions like naevi. For further readings performed after patch test removal, the transparency applied on the patient's back permits the attribution of a positive reaction. This method is clean (without ink marks on skin and without contamination of clothing), more comfortable for the patient (allowing back washing immediately after the 1st reading, never inducing allergy to inks), durable (permitting delayed readings after several days or weeks) and inexpensive (because transparencies can be reused).