Sunscreen following PDT; OTC hydroquinone

Q: What is the best sunscreen for use following photodynamic therapy (PDT)?

A more cosmetically acceptable alternative may be one of the beachwear sunscreens containing titanium dioxide (Neutrogena Sensitive Skin). Titanium dioxide is preferable because the particle size is larger than zinc oxide, producing more light reflection and scattering; however, some minor whitening of the skin may occur. If the patient won't tolerate this, one of the zinc oxide-containing facial moisturizers can be used (Olay Complete Defense SPF 30). If the patient wishes a completely transparent sunscreen, a stabilized avobenzone formulation can be recommended (Neutrogena Dry Touch SPF 55 with Helioplex).

A: Hydroquinone has been an extremely controversial ingredient in the United States as of late, but it has been controversial around the world for quite some time. Japan and the UK removed hydroquinone from the OTC market several years ago. Hydroquinone was one of the ingredients grandfathered by the Food and Drug Administration (FDA) when it was formed; therefore, the safety and efficacy of the OTC formulations have never truly been tested. There are a number of prescription formulations that have been FDA-approved through the IND process, and these products are not subject to FDA removal.

Apparently, the FDA was concerned about the use of OTC hydroquinone several years ago and asked the skincare industry to prepare a report demonstrating its efficacy and safety. The time for submission of the report passed, so the FDA proposed that all OTC hydroquinone products be removed from the market. Hydroquinone is a somewhat controversial substance. It is actually toxic to melanocytes and has been shown to produce cancer in an animal model when ingested orally. Hydroquinone is also a very potent oxidant causing oxidative damage to the skin accounting for its high irritant potential.

There is no doubt that hydroquinone is the most effective skin-lightening ingredient present on the market today, but perhaps its questionable safety profile means it should be limited to well-studied prescription formulations.

Zoe Diana Draelos, M.D., is a clinical associate professor of dermatology, Wake Forest University School of Medicine, Winston-Salem, N.C., and primary investigator, Dermatology Consulting Services, High Point, N.C. Questions may be submitted via e-mail to zdraelos@northstate.net
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