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Hair Loss: Infectious Agents

Folliculitis

Folliculitis is a term for inflammation of hair follicles. It looks like acne with little rings of inflammation surrounding the opening of a hair follicle. In the early stages of a folliculitis, the hair fiber may still be present, but as the folliculitis progresses the hair often falls out. When folliculitis is severe, inflammation is so intense that it can permanently destroy the hair follicles, leaving little bald patches.

There are non-infectious forms of folliculitis, such as those caused by oils and greases applied to the skin that clog up the hair follicles, but folliculitis is usually due to a bacterial infection. Particularly common is an infection of the hair follicles by Staphylococcus aureus. "Hot tub folliculitis" is caused by Pseudomonas aeruginosa which grows in inadequately chlorinated water.

Nonprescription topical antibiotics such as bacitracin, mycitracin, or neomycin can be used to treat minor folliculitis. For more serious infections, oral antibiotics such as erythromycin may be used.

Piedra

Piedra (trichomycosis nodularis) happens when the hair fibers are infected by a fungus. The visible indicator of a piedra infection is development of hard nodules on hair fibers. Indeed, "piedra" is Spanish for stone. The nodules are a concretion of hyphae and fruiting bodies of the fungus, known as an ascostroma, from which the fungal spores are released.

There are two basic types of piedra: black piedra and white piedra, referring to the color of the nodules formed on the hair fiber. Black piedra is due to the fungus Piedraia hortae and is mostly found in tropical countries, while white piedra is due to Trichosporon beigelii and is found mostly in Europe and Southern parts of the United States.

Piedra infection may affect hairs of the scalp, body, and genital areas. Usually the infection is relatively benign. In parts of Malaysia, the nodules of black piedra are considered attractive and traditionally women encouraged its growth by sleeping with their hair buried in the soil. However, when the infection is severe the fungus weakens the hair fiber, making it easy to break off. This can result in a patchy, diffuse hair loss.

Treatment generally involves shaving off affected areas. Anti-fungals such as ketoconazole or terbinafine are also used.

Demodex folliculorum

Some people believe Demodex folliculorum contributes to hair loss and that removing it will enable hair regrowth. But the organism does not cause hair loss.

Demodex is a little worm-like creature that likes to live on skin and in hair follicles. It feeds on dead skin and oils, so it particularly likes to live in hair follicles where there are lots of both.

Humans are born free of Demodex, but during childhood, through contact with others, the skin can become infected with it. For the most part, we never know they are there. They are benign, if repulsive, little creatures. The most common problem with Demodex is that they may cause irritation, particularly in the eyelashes. If you have itchy eyelashes, Demodex may be the problem.

However, this is as much as Demodex can do to you. It does not cause hair loss.

WebMD Medical Reference from the American Hair Loss Association

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