Comment on Botulinum Toxin for Androgenetic Alopecia

ABSTRACT

In the recent past, there has been a momentum for the treatment of androgenetic alopecia (AGA) with botulinum toxin (BTX), despite a lack of a scientific rationale and adequate medical evidence for its efficacy. The proposed modes of action of intradermal and intramuscular BTX for treatment of AGA are a relief of tension within the scalp area and relaxation of blood vessels and of arrector pili muscles (APM). However, there is so far no evidence that increasing the blood flow to the scalp increases hair growth. Moreover, there is no evidence that BTX has a hair growth-promoting effect either directly or through relaxation of the APM. Finally, studies with BTX in the treatment of AGA have not been convincing due to the absence of control groups, small numbers of participants, and low JADAD quality scores. In fact, a triple-blind randomized clinical trial failed to show any efficacy of BTX in male AGA. In our experience, intradermal BTX is effective for the treatment of either disabling hyperhidrosis of the scalp or of trichodynia by virtue of blocking the release of both of the neurotransmitters acetylcholine and neuropeptide substance P, respectively, from the neural axon endings.