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1. Background
During the past 15 years, a new mode of henna application, the so-called temporary black henna tattoo (TBHT), has become fashionable among children, adolescents and young adults. Generally, these types of tattoos are applied to young people in holiday resort areas (e.g., in Southern Europe, Turkey, Egypt, United States, Mexico, Australia, Southeast Asia and South Africa), at theme parks, festivals and fairs by artisan street tattoo artists with mobile studios [1].
In nature, black henna does not exist, but is derived from red henna (an orange pigment extracted from the Lawsonia inermis plants with a low potential for sensitization) mixed with various substances [2], among which the most important is para-phenylenediamine (PPD; i.e., a dye, that when dispersed, results in an intense black shade) [3,4,5]. The addition of PPD is essential to make the henna paste darker, longer lasting, more beautiful and more similar to henna without PPD. When PPD is in its oxidized form and at low concentrations, it does not have sensitizing effects, however, PPD is often added in henna tattoos in a non-oxidized form and in unknown concentrations, which can induce skin sensitization. Currently, the European Union prohibits the use of PPD in any topical product, with the exception of hair dyes, which may contain up to 6% [6]. The most common clinical manifestation of PPD sensitization is allergic contact dermatitis (ACD), which presents with erythema, blisters and bubbles at the area of application of the substance [7,8,9]. In the cases of ACD from TBHT, the dermatitis takes peculiar forms that reflect the tattoo design that has been applied. Sometimes serious systemic allergic reactions may occur [10,11,12].
Although TBHTs are usually considered harmless and temporary, in some cases they can produce permanent consequences. In addition, PPD is present in many everyday substances, whose exposure should be avoided in patients who have been previously sensitized. TBHT-related sensitization was uncommon in the paediatric population up until a few years ago. However, due to the increased use of tattoos, this condition is becoming an emerging issue, even during the first years of life. This report describes two paediatric cases of PPD sensitization and ACD after exposure to TBHT and summarizes the literature on this emerging clinical problem.
2. Case Presentation
A 9-year-old Caucasian...