Introduction: Henna tattoos are a very common practice in the adolescent population. Henna is very often admixed with para-phenylenediamine (PPDA) to improve the appearance of the tattoo. PPDA is a potent allergen, and is a frequent cause of allergic contact dermatitis (ACD). Material and method: A study was conducted on the results of 726 consecutive children who had been patch tested in the University General Hospital Consortium of Valencia between 1980 and 2015. Results: Almost half (49.7%; (361 cases) of the children had one or more positive patch test findings, with 4.7% (34) being allergic to PPDA. Mean age of patients allergic to PPDA was 12.4 years, and 44.2% were male. There were 2 cases (5.9%) of atopic dermatitis. Of the positive reactions, 73.5% were considered to be current clinically relevant. The sensitisation origin was a Henna tattoo in 50% of cases. Conclusion: PPDA sensitisation is relatively common in the child and adolescent population. The most frequent origin is the performing of Henna tattoos adulterated with PPDA. Adolescents are at the higher risk of developing ACD due to Henna tattoos. Henna tattooing should be strongly discouraged in children. (C) 2016 AsociaciOn Espanola de Pediatria. Published by Elsevier Espana, S.L.U. All rights reserved.