When injected into a given area Botox, which is the trade name of Botulinum toxin type A, reversibly blocks the impulses from the nerves to the tiny facial muscles that are related to expression lines. By doing this, the muscles cannot contract and therefore tend to relax. When muscles relax, the overlying skin remains smooth and unwrinkled while the untreated facial muscles continue to contract in a normal fashion, allowing normal facial expression to be unaffected.