Growth factors are one of the most controversial cosmetic ingredients in terms of safety. Recently, there was a legal challenge to a company that included spent culture media containing growth factors in its skin care products. A suit was brought stating that the growth factors were responsible for the induction of skin cancers because growth factors could promote growth of both normal and cancerous skin. The suit seemed to be a test case for a larger class action suit that would be brought on behalf of all individuals who developed skin cancer after using growth factor containing creams. Of course, demonstrating that the growth factor cream caused the skin cancers when skin cancers are common in the general population was challenging and the suit did not progress. Nevertheless, this lawsuit highlighted an interesting question. Are growth factors safe? In the past, it had been assumed that growth factors are safe because they are large molecular weight proteins that cannot penetrate the stratum corneum. Thus, their ability to contact the viable epidermis and dermis to impact living cells is limited.