A double‐blind,randomized assessment of the irritant potential of sunscreen chemical dilutions used in photopatch testing*

Background: The maximum concentration of organic sunscreen filters in current usage that does not lead to irritant reactions when performing photopatch testing is not known. Such irritant reactions can be misinterpreted as positive photoallergic contact dermatitis reactions. Objective: To determine the frequency of irritant reactions to 19 organic sunscreen filters in current use. Patients/Methods: Ninety‐four healthy volunteers were photopatch tested using the European consensus methodology to three different concentrations (2%, 5%, and 10%) of 19 organic sunscreen filters at the Photobiology Unit in Dundee, UK. Results: Of the 94 subjects recruited, 80 were analysed after withdrawals and exclusions. Of the 19 organic sunscreen filters studied, only 2 compounds led to irritant reactions in ≥5% subjects. Five per cent and 10% benzophenone‐4 led to irritant reactions in four and six subjects, respectively. Five per cent methylene bis‐benzotriazolyl tetramethylbutylphenol led to irritant reactions in six subjects, but unlike benzophenone‐4, this was not in a dose‐dependent fashion. Conclusions: When performing photopatch testing according to the European consensus methodology with these 19 organic sunscreen filters, a 10% concentration is suitable for all filters, except benzophenone‐4, which should be tested at a concentration of 2%.     

Photoprotection: a Review of the Current and Future Technologies

Exposure to ultraviolet (UV) radiation is associated with a variety of harmful effects ranging from photoaging to skin cancer. UVB (290 to 320 nm) directly damages the cellular DNA leading to the formation of the 6-4 cyclobutane pyrimidine dimmers, and UVA (320 to 400 nm) indirectly damages the DNA via the production of oxygen radical species. In this review, we focused on the technological and scientific aspects of photoprotection using sunglasses and clothing while attempting to dispel some of the misconceptions. In addition to the basic knowledge relating to sunscreens, we reviewed the current guidelines for testing and labeling UVA protection around the world, controversies associated with nanoparticles, and future sunscreens actives waiting for the Food and Drug Administration approval. Lastly, we reviewed alternative agents, such as antioxidants, that can be used to supplement and augment photoprotection provided by sunscreens.     

In Vitro Human Epidermal and Polyethylene Membrane Penetration and Retention of the Sunscreen Benzophenone-3 from a Range of Solvents

Purpose. To study epidermal and polyethylene membrane penetration and retention of the sunscreen benzophenone-3 (BP) from a range of single solvent vehicles and evaluate solvent effects on permeability parameters. Methods. The solubility of BP was measured in a number of solvents. Penetration of BP across human epidermis and high density polyethylene (HDPE) membranes was studied from 50% saturated solutions in each solvent. Results. Maximal BP fluxes from the solvents across the two membranes varied widely. Highest fluxes were observed from 90% ethanol (EtOH) for epidermis and from isopropyl myristate (IPM) and C_12–15 benzoate alcohols (C_12–15 BA) for HDPE membrane. Both the flux and estimated permeability coefficient and skin-vehicle partitioning of BP appeared to be related to the vehicle solubility parameter (_v). The major effects of solvents on BP flux appear to be via changes in BP diffusivity through the membranes. Conclusions. Minimal penetration of sunscreens such as BP is best achieved by choosing vehicles with a _v substantially different to the solubility parameter of the membrane.