In clinical medicine, percutaneous penetration has become a diagnostic reality, with evidence of the unintentional transfer of active gender hormones, i.e., estrogen and testosterone, from dosed to unknowing individuals occurring in clinical trials via interpersonal contact.1–4 Transfer depends on many factors, such as type of exposure, amount of transdermal hormone applied, number of exposures, applied area, transfer area, timing and frequency of contact.5 This unintentional transdermal hormone transfer may cause a clinically significant hormone imbalance and side effects such as cardiovascular events or masculinization in adults and precocious puberty or virilization in children.5–10
It is also possible that the transdermal transfer of applied hormones is of clinical relevance to personal care products. An estimated 1–3% of the population is allergic to a cosmetic product or ingredient contained therein.10 These allergies are mainly to fragrance chemicals such as hydroxy-isohexyl-3-cyclohexene carboxaldehyde and preservatives such as methyldibromo glutaronitrile, but also include emerging allergens such as UV filters and nail acrylates.11 Clinically significant reactions may range from mild sensory irritation to a clear allergy resulting in a positive patch test.11 Similar to transdermal hormone transfer, allergic dermatitis from a cosmetic product depends on many factors including composition of the product, concentration and purity of the ingredients, condition and site of application, contact duration and application frequency.11 The present overview examines the evidence validating transdermal hormone transfer and explores the potential for percutaneous penetration of cosmetic ingredients to cause dermatologic disease not only in the dosed individuals, but also in their interpersonal contacts.
