Hallucinated sensation that insects or snakes are crawling over the skin; a common side-effect of extensive use of cocaine or amphetamines WordNet 3.0 & Open English WordNet

Formication is the sensation resembling that of small insects crawling on the skin, in the absence of actual insects. Wikipedia

Abnormal sensation that bugs are crawling on or under the skin Wikidata

An abnormal skin sensation similar to that of insects crawling over or within the skin; a tactile hallucination involving such a sensation. A common side-effect of substance abuse, it can also be experienced with high fever, menopause, skin cancer, diabetic neuropathy, or herpes zoster. Wiktionary