Many toxic plants are unpalatable, so animals avoid them where possible. However, this is not always the case; locoweeds, for example, are addictive and once a horse has eaten them, it will continue to eat them whenever possible, and can never be exposed to them again.
Micrograph of melanosis coli, with the characteristic mucosal lipofuscin-laden macrophages (brown). Melanosis coli, also pseudomelanosis coli, is a disorder of pigmentation of the wall of the colon, often identified at the time of colonoscopy.It is benign, and may have no significant correlation with disease. The brown pigment is lipofuscin in macrophages, not melanin.urther information: Factitious diarrhea. The most common cause of melanosis coli is the extended use of laxatives, and commonly anthraquinone containing laxatives such as Senna and other plant glycosides.
Hyperpigmentation can be caused by sun damage, inflammation, or other skin injuries, including those related to acne vulgaris. People with darker skin tones are more prone to hyperpigmentation, especially with excess sun exposure. Many forms of hyperpigmentation are caused by an excess production of melanin. Hyperpigmentation can be diffuse or focal, affecting such areas as the face and the back of the hands. Melanin is produced by melanocytes at the lower layer of the epidermis.