The retrospective multicenter observational study published in this issue of Actas Dermo-sifiliográficas by members of the Spanish Research Group on Contact Dermatitis and Skin Allergies (known by its Spanish acronym, GEIDAC) shows that the frequency of sensitivity to p-phenylenediamine (PPD) among patch-tested patients is about 4%,1 a figure that has held steady in recent years in spite of legislation to reduce the concentration of PPD in hair dyes. Although hair dyes are not the only source of exposure to PPD, they are the main culprits for both staff and customers of hair salons. Some have called for PPD to be removed from the Spanish standard series recommended by the GEIDAC because of the risk of sensitization through testing. However, such risk appears to be very low, and the high rate of sensitization detected in Spanish patch tests1 fully justifies continuing to include this compound in the series.

Exposure to PPD through black henna preparations merits special mention, given the widespread use of this substance for temporary tattooing. The real frequency of PPD sensitization through this means is unknown, but nearly all dermatologists who treat contact dermatitis have diagnosed several cases traced to this source in recent years. Stricter control of temporary tattooing should be introduced, and the use of PPD in henna preparations should be prohibited, or at the very least, the concentration should be reduced. Efforts should also be made to raise public awareness of the risks posed by temporary tattooing.