ABSTRACT
Seeking shade and covering-up are the top two means of sun protection. The ideal
sunscreen should protect similarly, i.e., uniformly protect against UVB and UVA
radiation. The four requirements for good UV protection are (i) technology, (ii)
assessment of performance, (iii) standard, and (iv) compliance. The highest UVA
category (4 stars) of the Food and Drug Administration (FDA)-proposed rule (Federal
Register, 27 Aug 2007) is already very close to the ideal sunscreen. Absorption is the
major mechanism of protection by UV filters. Scattering of particulate UV filters
contributes a maximum of 5% to 10% to the protection; a higher percentage would lead to
the undesired “whitening effect.” The UV filters available in the United States absorb
mainly in the UVB/UVA-II range. Avobenzone is the only efficient UVA-I filter in the
United States. At the time of this writing, four additional UVB and two broad-spectrum
UV filters are awaiting FDA approval. The design of UV filters is described with the
example of development of the broad-spectrum UV filter bemotrizinol. Variation of
substituents to the aromatic ring system of the molecule leads to photostabilization and
different UV absorption spectra. The molecular weight of all new UV filters that are not
yet available in the United States is generally higher than 500 Dalton.
