Formication is a prickling sensation that resembles the feeling of ants crawling over the sufferer's skin. It can be described as a tactile hallucination. The most common locations are the hands, arms, legs and neck.

The most common cause is not menopause, but drug or alchohol overdose. Formication is also very common amongst people using "normal" amounts of methamphetamine. Some schizophrenics also experience formication.

In cases in which formication accompanies something where judgement is impaired, such as drug use, a common effect is for the sufferer to scratch at their skin violently, believing there to be something underneath in an attempt to stop the sensation. The skin is often broken by this.