Plastic surgeons who were injecting Botox for facial wrinkles found that many of their patients reported improvement in headaches. Prolonged muscle contraction, spasms, and inappropriate tone are thought to diminish blood supply and increase oxygen demand. Ischemic muscle is believed to make pain-producing substances, which further irritates the muscle and causes spasms. The simplest explanation for the mechanism of action for treating headaches is relaxation of the muscles that trigger headaches. When Botox is administered, important considerations include the amount injected per muscle, the total amount injected, the number of sites injected, and selection of appropriate areas to inject. Botox is best administered by clinicians experienced in using it.