Azelaic acid is a naturally occurring substance that studies have shown to inhibit 5-alpha-reductase in human skin. 5-alpha-reductase converts testosterone into dihydrotestostrone (DHT), accumulation of which in scalp is believed to be responsible for the male pattern hair loss. Inhibition of this enzyme by azelaic acid can reduce the concentration of DHT in scalp and therefore stimulate hair regrowth. Azelaic acid can be found in many prescription acne medications. Azelaic acid is added to minoxidil solutions in hair loss treatment products because it has different mechanism of action in preventing hair loss.