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LUCA uses Avobenzone which has been stabilized and strengthened by PolycryleneŽ. This increased UVA protection is reflected in our critical wavelength, which is the highest in the U.S. market. Critical wavelength is an internationally recognized rating system for UVA protection which will likely be adopted by the FDA at some point in the future.

*Critical Wavelength:


Critical wavelength is an international rating system for UVA protection. It is a measurement performed on a machine in which sunscreen is applied to a slide. The slide is then irradiated from an artificial light source to simulate sun exposure. Exposure begins at 290nm, with subsequent exposure to progressively higher wavelengths of light. The point at which the sunscreen allows 10% of the rays to penetrate through the slide is defined as the critical wavelength. Another way of looking at this, would be this is the point where the level of protection provided by the sunscreen has dropped, to the point where only 90% of the rays are blocked (absorbed). The advantage of the critical wavelength is that it is an in vitro, very reproducible laboratory test. A sunscreen with a critical wavelength over 370nm is considered by the FDA to provide excellent UVA protection. View the Science of Critical Wavelength

Providing a UVA rating system such as critical wavelength is essential in allowing consumers to select products that provide appropriate levels of UVA protection. However when measuring critical wavelength, it is important that this measurement be performed on a sample that has been irradiated. This provides proof that the formulation is stable when exposed to intense sunlight. LUCA is photostable. The level of radiation used equivalent to 4-6 hours of intense sun.