The Science of Botox

How Botox Works to Reduce Wrinkles

Woman getting Botox
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Injection of Botulinum toxin type A, or Botox, is the most common non-surgical cosmetic procedure performed in the United States. Even with its popularity, there are still many myths and misinformation about this procedure. The most common myth is that people who get Botox are being injected with botulism. This article explains the science of Botox.

The History of Botox

The bacteria, Clostridium botulinum, produces a toxin that actually contains 7 distinct serological types.

Type A is the most potent and is marketed by Allergan as Botox. Type B is marketed by Elan Pharmaceuticals as Myobloc. Botulinum toxin types A and B have been FDA approved for various indications.

  • 1989 - Type A approved for treatment of strabismus and blepharospasm.
  • 2001 - Type A & B approved for treatment of cervical dystonia
  • 2002 - Type A approved for the cosmetic treatment frown lines between the eyebrows only

How Botox Works

The medical term for the action of Botox is selective muscle denervation. Normally, to make a muscle contract, a nerve sends a signal to the muscle. The point where the nerve and the muscle meet is called the neuromuscular junction. When the signal gets to the neuromuscular junction a chemical called acetylcholine is released from the nerve side of the junction and binds to the muscle side of the junction causing more chemical reactions that make the muscle contract.

Botox works by blocking the acetylcholine receptors on the muscle side of the junction. Then when the nerve sends a signal to the muscle to contract, acetylcholine is released as before, but it can't bind anywhere on the muscle. The muscle has no idea it is supposed to contract. It is essentially paralyzed, but not because it or the nerve have been damaged.

This acetylcholine blockade is not reversible and begins within 48 hours. The clinical effects of a Botox injection become noticeable between 5-10 days. Over the next 3-5 months the muscle gradually develops new receptor sites and is able to contract again.

Botox and Wrinkles

When Botox is injected into a muscle that causes a wrinkle in the overlying skin when it contracts, paralysis of that muscle prevents the wrinkle from forming. The effects of Botox are most noticeable in dynamic wrinkles, or wrinkles that are only present when the muscle contracts.

As we get older and lose elasticity in the skin, a permanent crease can form leaving a wrinkle that is noticeable even without muscle contraction. Botox does not get rid of these wrinkles, but may help soften them.


Gordon ML. "A Conservative Approach to the Nonsurgical Rejuvenation of the Face." Dermatologic Clinics 2005;23:365-371.

Botulinum Toxin (Botox Cosmetic) for Frown Lines. The Medical Letter 2002;44:47-48

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