Is there a risk of active sensitization to PPD by patch testing the general population?

Area of Science:

• Dermatology
• Allergology
• Epidemiology

Background:

• Para-phenylenediamine (PPD) is a common ingredient in permanent hair dyes.
• PPD can cause allergic contact dermatitis in susceptible individuals.
• The safety of PPD patch testing in population-based studies has been a concern.

Purpose of the Study:

• To evaluate the safety of repeated patch testing with PPD in a general population cohort.
• To determine if PPD patch testing can induce sensitization in individuals without prior reactions.

Main Methods:

• The Glostrup allergy studies conducted two patch tests with PPD on the same cohort.
• In 1990, 567 individuals were tested; in 1998, 365 of the original participants were re-tested.
• Participants with no or only one previous positive reaction were included in the safety assessment.

Main Results:

• In the initial 1990 study, only one participant showed a positive reaction to PPD.
• In the 1998 re-test, no positive reactions to PPD were observed among the participants.
• The repeated patch testing did not lead to new cases of PPD allergy.

Conclusions:

• Patch testing with PPD is safe for individuals with no or only one previous positive reaction.
• Repeated PPD exposure through patch testing in this context does not appear to cause active sensitization.
• PPD patch testing can be safely utilized in epidemiological studies with minimal risk.