Hair loss is typically caused by male or female pattern baldness, which account for most baldness cases in both sexes. There are, however, several infectious agents can cause hair loss, usually temporarily. Hair loss caused by an infectious scalp condition usually resolves when the cause of the infection is addressed.
There are a umber of infections that can cause hair loss:
Sometimes known as hot tub rash or barber's itch, this condition is an infection or inflammation of the hair follicles. Symptoms include a rash, pimples or pustules located around hair follicles as well as itchy skin. The affected hair follicles often fall out, and severe folliculitis can lead to the formation of permanent bald patches. Folliculitis can affect any part of the body except for the palms of hands and the soles of the feet.
This condition is usually caused by a bacterial infection with Staphylococcus aureus or Pseudomonas aeruginosa.
Certain fungal and viral infections also cause folliculitis. The Herpes Simplex virus, for instance, can infect hair follicles and cause folliculitis, notably around the mouth. Some rare non-infectious disorders such as Folliculitis decalvans, Folliculitis keloidalis or Pseudofolliculitis barbae can also cause folliculitis.
The treatment of folliculitis is usually topical, with an antiseptic or antibiotic that addresses the bacteria, viruses or fungi that are causing the inflammation of the hair follicles. Some patients might also be prescribed a course of systemic narrow-spectrum penicillinase-resistant penicillin. Fungal folliculitis is usually treated with an oral anti-fungal medication.
This fungal infection can develop on any part of the body (athlete's foot is a relatively common manifestation). When it develops as a scalp condition it is also known as tinea capitis.
The various fungi that cause ringworm feed on the keratin of the hair and skin and can easily move from person to person or from a pet to its owner by skin-to-skin contact.
Ringworm symptoms include hair breakage and hairless scaly patches. These patches are usually itchy, blistered, red and inflamed around the outside, creating the appearance of an inflamed ring that surrounds a more normal patch of bald skin.
Ringworm treatment is focused on the particular fungus involved in the infection. The treatment of choice for most ringworm cases is griseofulvin, an inexpensive anti-fungal which binds with keratin and blocks the fungus from infecting it.
This infection causes the development of hard nodules filled with fungal hyphae and fruiting bodies on the hair fibers. Interestingly enough, these hard “stones” (either black or white, depending on the responsible fungus) are considered attractive in certain regions of Malaysia and women go though a lot of effort to encourage the fungi to grow on their hair.
The severe cases of piedra, however, are not particularly attractive: the fungus gradually weakens the hair fibers and causes hair to fall in patches or diffusively all over the scalp.
Piedra is treated by shaving off the affected areas. Dermatologists might also prescribe a course of anti-fungals.
Some studies suggest a link between a lesser-understood type of alopecia – alopecia areata – and untreated dental infections.
Bald patches caused by teeth infections can appear in a line or above a line projected from the affected tooth. They can appear on the scalp, beard or eyebrows. In some cases hair will re-grow after a few weeks, but sometimes the condition can instead cause further hair loss on the scalp or on the body.
Alopecia areata is considered an autoimmune disease that causes the hair follicles to be mistakingly attacked by the immune system.
The association with dental infections might be good news for alopecia areata patients: once the initial infection is treated, the bald patches will usually be much easier to treat or reverse, especially if the infection is caught in the early stages.
This inflammatory skin condition causes scaly, itchy, inflamed skin that can become painful to touch.
Since seborrheic dermatitis sometimes causes oily skin, a symptom of the production of sebum rich in triglycerides and cholesterol that encourages the proliferation of yeasts on the skin. Pityrosporon ovale can sometimes increase in numbers in severe seborrheic dermatitis cases and can in turn cause further irritation and inflammation and diffuse hair loss in the affected areas.
The proliferation of yeasts on the skin is not an infectious condition as such, however, since it cannot be caught from or transmitted to others.
Get in touch with an experienced dermatologist or hair specialist as soon as possible if you suspect a bacteria, virus or fungus is responsible for your hair loss: most infectious scalp conditions that cause the loss of hair are reversible especially if treated early.