Stability of sunscreens and sunblocks following exposure to extreme temperatures

摘要

To the Editor: Sunscreens and sunblocks are significant means of protection from the cutaneous damages imparted by ultraviolet radiation (UVR). Chemical sunscreens, as opposed to physical sunblocks, typically consist of a combination of lipophilic organic compounds in order to absorb the broad UVR spectrum. These sunscreen oils are incorporated into the lipophilic phase of oil-in-water or water-in-oil emulsions to achieve an efficacious and esthetically acceptable product.1 Sunscreens are frequently exposed to temperature extremes. For example, depending on the ambient temperature, the interior temperature of an automobile can range from —3°C to 89°C.2'3 These extreme temperature exposures may have a profound effect on the chemical stability of sunscreens and induce irreversible emulsion instability via alteration of droplet-droplet interactions and phase transitions.4 These physical and chemical changes could reduce the ability of sunscreens to protect the skin by filtering and/or absorbing UVR.