Topically applied L-carnitine effectively reduces sebum secretion in human skin.

Summary Background  Oily skin condition is caused by an excessive sebaceous gland activity, resulting in an overproduction of sebum, giving the skin an undesired shiny, oily appearance. Aims  To identify an active substance that reduces sebum production in human sebaceous glands by regulating fat metabolism in a natural way. Patients/Methods  The effects of l-carnitine on β-oxidation and intracellular lipid content were investigated in vitro using the human sebaceous cell line SZ95. Penetration experiments utilizing pig skin as a model system were performed with a cosmetic formulation containing radioactively labeled l-carnitine. To determine the in vivo effects, a vehicle-controlled, randomized study was carried out using a cosmetic formulation containing 2%l-carnitine for 3 weeks. Sebum production was investigated utilizing the lipid-absorbent Sebutape®. Results  SZ95 cells treated with 0.5% or 1%l-carnitine demonstrated a significant concentration-dependent increase in β-oxidation compared to control cells. Following the treatment with l-carnitine, intracellular lipid concentrations decreased significantly in a dose-dependent manner compared with untreated control cells. In skin penetration experiments, topically applied l-carnitine reached the dermis. In addition, topical in vivo application of a formulation containing 2%l-carnitine for 3 weeks significantly decreased the sebum secretion rate compared to the treatment with vehicle. Conclusions  Our results show that the treatment of human sebocytes with l-carnitine significantly augments β-oxidation and significantly decreases intracellular lipid content in human sebocytes. Topically applied l-carnitine is bioavailable and leads to a significant sebum reduction in vivo. In conclusion, l-carnitine represents a valuable compound, produced naturally within the body, for the topical treatment of oily skin in humans.