First, to significantly reduce oil production, very large areas of the face would need to be treated, resulting in the expressionless look for which Botox is often mocked.
Second, the procedure is difficult. Even Dr. Shah admits that "Experience here is really essential.“ The muscle paralyzer has to be injected directly into a layer of skin just 1/25th of an inch thick. If it's injected too deeply it can alter the patient's facial expressions.
Third, Botox as an acne treatment can be prohibitively expensive. Once you find a doctor willing to treat your break-outs in this way, a treatment can cost upwards of $500 and last for only 4 months.