Hair Loss: Infectious Agents
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 (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.