An abnormal skin sensation similar to that of insects crawling over or within the skin; a tactilehallucination 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.
The initial indications of the disease were cutaneous itching, tingling and formication, which gave place to actual loss of cutaneous sensation, first observed in the extremities.
Secondly, there are so-called " subjective sensations," without any external object as stimulus, most commonly in vision, but also in touch, which is liable to formication, or the feeling of creeping in the skin, and to horripilation, or the feeling of bristling in the hair; yet, even in " subjective sensations," we perceive something sensible, which, however, must be within, and not outside, the organism.
But sooner or later peripheral neuritis develops, usually beginning with sensory disturbances, tingling, numbness, formication and occasionally cutaneous anaesthesia.