As a dermatologist, I see lots of itchy people and since I work in an urban HIV clinic, I see lots of methamphetamine users/abusers. Hopefully I can clarify some of what has been said already in this thread.
There are people who have never touched methamphetamine (or heroin, cocaine, etc) that scratch the hell out of themselves. Sometimes, an underlying internal or skin-associated cause is responsible (e.g. skin lymphoma, kidney failure, atopic dermatitis, scabies, and many others). Sometimes there is no apparent cause. These patients fall under the diagnostic category of neurodermatitis.
My residency mentor wholly believed that neurodermatitis is a disorder fundamentally linked to the “itch-scratch cycle,” wherein, chronically scratched skin becomes itchier. It is thought that neurological mechanisms (both in the skin and the CNS) underlie this physiology.
The changes induced by chronic scratching exist along a spectrum from mere color changes (macular amyloid), to thickening of the rubbed and scratched skin (lichenification, prurigo nodularis, lichen amyloidosis), and finally to the patients typically depicted in the anti-drug brochures with ulceration and erosion of the skin (neurotic excoriations).
The degree of insight that patients possess with regard to the cause of these conditions is also variable. Most acknowledge that they scratch the affected area often. What’s fascinating is that the compulsion to scratch is all but irresistible and in many cases requires psychotropic medications to overcome. Some patients deny any role in creating this condition. A smaller minority become convinced that an unknown parasitic infestation is responsible (Morgellon’s disease or delusions of parasitosis). This group is the most challenging to treat and have a poor prognosis unless convinced to start taking anti-psychotics (at low doses compared to standard treatment doses for “true” psychotic disorders).
So where does methamphetamine come into play? My belief is that methamphetamine is a catalyst in individuals otherwise prone to compulsive scratching. Scratching/picking at the skin probably is tied to a grooming instinct and therefore at a certain threshold is beneficial/of no harm. The threshold likely has an as of yet unknown genetic basis and varies in the population. IMHO, methamphetamine use pushes the individual towards the pathological end of the grooming/picking spectrum.
Certainly not all users are severely affected, though in my opinion the incidence of picking/scratching induced skin disease is higher in this population. Additionally, in many patients, the problem does not subside with cessation of the drug use. One of the most memorable patients from my residency was a 40 year old male who thought bugs were crawling on his skin. He was a former methamphetamine user but hadn’t done drugs in 10 years. This condition was so bothersome that he contemplated suicide several times. He often soothed his skin with alcohol or witch hazel, but most memorably, he sometimes resorted to Black Flag ant & roach spray.
:eek:
