Sun rays damage unprotected skin. Substances in medications or lotions applied to the skin can be chemically modified by sun rays to have a toxic effect on the body. Experts call the phenomenon phototoxicity. A new accredited in-vitro test method measures the phototoxic potential of substances or cosmetics. Thanks to this test, performed on a fully developed epidermis model, companies can examine the phototoxicity of a substance with an in-vitro ISO certified methodology, improving cosmetics safety.