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

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.