Smokers melanosis is seen with the naked eye as a brown to black pigmentation of the oral tissue i.e. the gums, cheeks or palate  as well as in larynx. It is most often seen in the lower labial gingiva of tobacco users. Most easily it is found in Caucasians, due to their lack of a genetically caused melanin pigmentation.The brown to black colour is melanin. In skin, melanin prevents harmful UV-light from reaching deeper, sensible parts of the tissue. If UV-light penetrates deep, some of the toxic substances due to the UV-light damage to the cells, are bound to melanin in the epithelial cells and travel with the ageing cells to the skin surface, where they are expelled from the tissue surface. In this way the melanocytes and keratinocytes together protect the tissue, with melanin serving as a toxic defence and cleaning agent. In the oral mucosa, where the ageing epithelial cells move faster to the surface compared to skin, a similar defence-mechanism seems to be present, cleaning the mucosa from different toxic chemicals penetrating the epithelium. Besides chemicals in tobacco  also antimalaria-drugs cause an oral pigmentation. Smokers melanosis is like the genetic melanin pigmentations, a defence-system in action. The microscope shows smokers melanosis to be characterized by a melanin hyperpigmentation of the lower part of the oral epithelium, similar to sun-tanned skin. The hyperpigmentation consists of melanin granules which have the shape and colour of "coffea beans".
Crotamiton is a drug that is used both as a scabicidal (for treating scabies) and as a general antipruritic (anti-itching drug). It is a prescription, lotion-based medicine that is applied to the whole body to get rid of the scabies parasite that burrows under the skin and causes itching. Use
For treating scabies, crotamiton should be applied to the whole body rather than a localized area. It is applied two or three times, with a 24-hour delay between applications, and the patient is asked to take a shower no sooner than after 48 hours. For children under 3 years, it is applied once daily. It can also be used to treat itching stemming from other causes, e.g. insect bites, in which case it is applied to the itching areas only, and repeated if necessary after 4 to 8 hours. Use near the eyes, or breaks in the skin, should be avoided. Pharmacology
Crotamiton is toxic to the scabies mite. It probably acts as a general antipruritic by inhibition of TRPV4, a sensory ion channel that is expressed in the skin and primary sensory neurons. Pharmacokinetics
After topical application, crotamiton is absorbed systemically. It has an elimination half-life of 30.9 hours and 4.8-8.8% is excreted in the urine. Side effects
The most common side effect of crotamiton is skin irritation. Trade name
Crotamiton is marketed under the trade names Eurax, which is manufactured by Ranbaxy Laboratories in the United States, and GlaxoSmithKline in the United Kingdom, and Euracin, which is manufactured by Green Cross in South Korea.