Before leaving the subject of TE, here are a few words about natural hair shedding. Everyone sheds hair and you may see more hair shed at certain times of the year. Studies show that humans, at least in Northern Europe away from the equator, shed more hair in the fall and to a lesser extent in the spring.
This temporary increase in the number of telogen hair follicles and shed hair is probably due to changes in hormones in response to changes in daylight exposure. Studies in mink and other mammals show that daylight exposure significantly alters prolactin levels and that prolactin has a significant effect on molting. As with mink and other mammals, humans probably have much the same molting response. Such hair loss should be temporary.
Anagen effluvium is a diffuse hair loss like telogen effluvium, but it develops much more quickly and can cause individuals to lose all their hair. Anagen effluvium is most frequently seen in people taking cytostatic drugs for cancer or those who have ingested toxic products like rat poison.
Substances of this type inhibit rapid cell proliferation. This is a desirable factor if you are trying to block the development of a cancer, but the cells of hair follicles are some of the most rapidly proliferating, noncancerous cells the body has. Hair fiber from scalp hair follicles grows at up to 0.4mm a day and that rate of growth requires a lot of cell proliferation. Cytostatic cancer drugs and various toxins and poisons inhibit rapid cell growth, including the proliferation of cells in the hair follicles. The result is a sudden shut down of hair fiber production.
The onset of anagen effluvium is very rapid. Some individuals who start taking anti-cancer drugs can literally pull their hair out in clumps within the first two weeks. Because these drugs act so quickly and are so potent, the hair follicles have no time to enter into a telogen resting state, as with telogen effluvium, a response to a more moderate environmental challenge.