Percutaneous penetration and pharmacodynamics: Wash-in and wash-off of sunscreen and insect repellent

Abstract

Increased awareness of skin cancer and mosquito-transmitted diseases has increased use of insect repellents and sunscreens. The challenge in setting recommendations for use and reapplication, especially when used concomitantly, lies in finding the balance between applying a durable product effective in withstanding natural and physical factors such as water, sweat, temperature and abrasion, while limiting percutaneous absorption and decreasing risk of potential dermal and systemic toxicity. Inorganic sunscreens show no or little percutaneous absorption or toxic effects in comparison to organic sunscreens, which show varying levels of dermal penetration and cutaneous adverse effects. An alternative to N,N-diethyl-m-toluamide (DEET), the traditional gold standard compound in insect repellents, picaridin appears as efficacious, has lower risk of toxicity, and when used simultaneously with sunscreen may decrease percutaneous absorption of both compounds. Conversely, combined use of DEET and sunscreen results in significantly higher absorption of both compounds. It is important to increase consumer awareness of "washing in" of various compounds leading to increased risk of toxicity, as well as differences in reapplication need due to "washing off" caused by water, sweat and abrasion. Although much remains to be studied, to maximize efficacy and decrease toxicity, contemporary research tools, including dermatopharmokinetics, should aid these prospective advances.

ZnO nanoparticles and organic chemical UV-filters are equally well tolerated by human immune cells

“…This estimation is based on a standard test sunscreen dose of 2 mg/cm 2 (Gulson et al 2010;, and the respective concentrations of UV-filters in sunscreens coupled with the amount of transdermal penetration (organic UV-filters at the aforementioned 5 -15 wt% of the formulation, with transdermal penetration rates up to 8%; compared with ZnO at 20 wt% of the formulation, with penetration rates of <0.1%). It should J U S T A C C E P T E D also be noted that consumers commonly apply less than the recommended amount of sunscreen (between one-half to one-fifth), so the localised penetration dose would be expected to be lower (Gulson et al 2015;Rodriguez & Maibach 2016). Also, as the transdermal penetration of zinc from particulate UV-filters is at least an order of magnitude less than that of organic UV-filters, their similar bioactivity dose response profiles in human immune cells indicates that NPs have at least an order of magnitude lower potential risk for eliciting these effects in vivo.…”

“…Although these chemicals are small lipophilic molecules that would be expected to diffuse through the epidermis more rapidly, sunscreens are formulated to stay on the skin's surface and this greatly limits their absorbance through the skin (Rodriguez & Maibach 2016).…”

Neurotoxic effect of active ingredients in sunscreen products, a contemporary review

“…Similar findings were reported following a 4-day exposure to these ingredients, which were detectable in the plasma of human males and females merely 2 h following application [20] . More data on human skin penetration and distribution of various UV filters, both organic and inorganic, can be found in recent reviews [21] , [22] , [15] .…”

¿Son efectivos los repelentes contra mosquitos para prevenir enfermedades transmitidas por vectores?

“…Sin embargo, ensayos de campo hechos en Australia usando icaridina al 19,2% y DEET al 35% dos veces al día, señalan a la icaridina como mejor aceptada ya que sería menos grasosa y pegajosa que el DEET [4] .No se han reportado efectos tóxicos notorios para repelentes como DEET, icaridina o IR3535 a concentraciones recomendadas, por lo que la OMS no restringe su uso en gestantes y niños [2] . El DEET ha sido el repelente más estudiado en cuanto a reacciones adversas, pero la mayoría de las reacciones que fueron reportadas estuvieron asociadas a ingestión del químico o por el uso de concentraciones altas sobre la piel (70%), por ello desde su aprobación sigue siendo el repelente de elección y es considerado como el Gold standard [5] .Los nombres comerciales, el tiempo de protección y las concentraciones más comunes de los repelentes disponibles en nuestro medio se muestran en la Tabla 1 [1] .Respecto al uso simultáneo de protector solar (como oxibenzona) y repelente (DEET o icaridina), este no es recomendable, ya que tienen distintos mecanismos de acción y frecuencia de uso; pudiendo incrementar la absorción de ambos químicos o reduciendo la penetración dérmica; y con ello un riesgo de reacciones en la piel, por lo que se sugiere primero aplicar el protector solar y después de unos diez a veinte minutos aplicar el repelente, y reaplicar según indique la etiqueta del producto [6] . a Licenciada en enfermería; b Bióloga ¿Son efectivos los repelentes contra mosquitos para prevenir enfermedades transmitidas por vectores?…”

“…Respecto al uso simultáneo de protector solar (como oxibenzona) y repelente (DEET o icaridina), este no es recomendable, ya que tienen distintos mecanismos de acción y frecuencia de uso; pudiendo incrementar la absorción de ambos químicos o reduciendo la penetración dérmica; y con ello un riesgo de reacciones en la piel, por lo que se sugiere primero aplicar el protector solar y después de unos diez a veinte minutos aplicar el repelente, y reaplicar según indique la etiqueta del producto [6] . a Licenciada en enfermería; b Bióloga ¿Son efectivos los repelentes contra mosquitos para prevenir enfermedades transmitidas por vectores?…”