Marrying ophthalmology to dermatology, Jean and Alistair Carruthers observed that blepharospasm patients who received injections around the eyes and upper face also enjoyed diminished facial glabellar lines (“frown lines” between the eyebrows), thereby initiating the highly-popular cosmetic use of the toxin. Brin, and a group at Columbia University under Monte Keen made similar reports. In 2002, following clinical trials, the FDA approved Botox Cosmetic, botulinum A toxin to temporarily improve the appearance of moderate-to-severe glabellar lines. The FDA approved a fully in vitro assay for use in the stability and potency testing of Botox in response to increasing public concern that LD50 testing was required for each batch sold in the market.
Though there's still more research to be done on Botox for migraines and doctors aren't yet completely sure why the procedure is effective, they have some ideas. Ravitz tells me, "What [Botox] does is paralyze nerve terminals. Essentially, nerve terminals transmit pain, but they also produce pain substances while they’re doing that, and it completely paralyzes that process." She says that it stops the process of pain patterning and it also relaxes the muscles.
Spread of toxin effects. The effect of botulinum toxin may affect areas away from the injection site and cause serious symptoms including: loss of strength and all-over muscle weakness, double vision, blurred vision and drooping eyelids, hoarseness or change or loss of voice, trouble saying words clearly, loss of bladder control, trouble breathing, and trouble swallowing.