Hair Loss: Infectious Agents

A number of infectious agents and infection-related conditions can contribute to hair loss. Some common ones are described here.

Ringworm

Surprisingly, ringworm has nothing to do with worms, but is a fungal infection that can occur anywhere on the body. If it develops on the scalp, it can cause patches of hair loss and is known to doctors as “tinea capitis.” Ringworm is the same thing as athlete’s foot, and the same kind of fungal infection that can affect the nails too.

On the scalp, ringworm usually begins as a small pimple that progressively expands in size, leaving scaly patches of temporary baldness. The fungus gets into the hair fibers in the affected area and these hairs become brittle and break off easily, leaving a bald patch of skin. Affected areas are often itchy, red, and inflamed, with scaly patches that may blister and ooze. The patches are usually redder around the outside with a more normal skin tone in the center. This may create the appearance of a ring — hence the name, ringworm.

Worldwide, the fungus Microsporum audouinii is a very common cause of ringworm, but increasingly Trichophyton tonsurans can also cause tinea capitis, especially in the US and Latin American countries. Other fungi that may cause tinea capitis include Trichophyton schoenleinii and Trichophyton megninii in Southern Europe and Africa, and Trichophyton violaceum in the Middle East.

The fungus Microsporum gypseum can also sometimes cause tinea capitis. This fungus is common in soil and may be transferred to humans by contact with infected animals. You can also get ringworm from pets that carry the fungus, and cats in particular are common carriers. Ringworm is contagious. It can be passed from one person to the next by direct skin-to-skin contact. You can also catch ringworm through contact with contaminated items such as combs, unwashed clothing, and shower or pool surfaces.

Treatment for ringworm varies depending on the particular fungus involved. Some types of ringworm infection will go away spontaneously and no treatment is given. However, most commonly, griseofulvin, an anti-fungal, is used. Griseofulvin is very effective against fungi in hair and skin but it is not so good at treating yeast or bacterial infections. The drug gradually accumulates in the skin and hair. It especially likes to bind with keratin, which is a key component of hair, skin, and nails, and blocks the fungus from infecting the keratin.

More recently, some fungi that cause tinea capitis show some resistance to the drug, which means higher doses and longer courses of treatment. As an alternative to griseofulvin, newer anti-fungal drugs like terbinafine, itraconazole, and fluconazole can be prescribed.

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.

Seborrheic Dermatitis

Seborrheic dermatitis is first and foremost a skin condition, but it can involve infection and temporary hair loss if the dermatitis is located on the scalp or other skin areas. The dermatitis causes scaly, sometimes oily, inflamed skin that can be itchy or even painful to touch.

This is an inflammatory condition that is not well understood, although there does seem to be a genetic component and Caucasians, particularly of Celtic descent, are most susceptible. Some newborns develop seborrheic dermatitis when maternal androgens are passed from the mother to the baby across the placenta. Conditions such as Parkinson’s disease, head injury, and stroke can also be associated with seborrheic dermatitis, and stress and chronic fatigue can make it worse. Times of hormone fluctuation, such as during puberty, can activate the onset.

In part, the trigger for seborrheic dermatitis may be androgen steroids. The sebaceous glands attached to the hair follicles begin to produce a very rich form of sebum. The sebum contains fewer free fatty acids and squalene but increased amounts of triglycerides and cholesterol. The excess, rich sebum production triggers the proliferation of skin flora. Yeast Pityrosporon ovale (also called Malassezia furfur) has been shown to increase in numbers with the intensity of seborrheic dermatitis. This excessive yeast proliferation causes more irritation and inflammation.

Although all this inflammation is not specifically directed at the hair follicle, if hair follicles are in the vicinity of the inflammatory cells then they can be affected. Hair follicles find inflamed skin an unhealthy environment in which to grow. Thus seborrheic dermatitis may non-specifically cause diffuse hair loss.

Although seborrheic dermatitis can involve a proliferation of yeast, seborrheic dermatitis is not infectious — you cannot catch seborrheic dermatitis. Where yeast is involved in seborrheic dermatitis it comes from the affected individual’s own skin. We all have yeasts of various types living on our skin — the problem in seborrheic dermatitis is that the yeasts may grow to far greater numbers than normal.

Treatments

There are several treatments for seborrheic dermatitis. The simplest involves medicated anti-dandruff type shampoos to control the skin proliferation and scaling. Several shampoos might be recommended for alternating use on different days and each with its own particular activity.

Shampoos for seborrheic dermatitis may contain sulfur, selenium sulfide, zinc pyrithione, tar, salicylic acid, or oil of cade. These shampoos have been available for many years. More recently azole-based shampoos (such as ketoconazole [brand name: Nizoral]) have been made available over the counter. All can be effective in treating seborrheic dermatitis.

Some dermatologists may also prescribe antibiotics to control the skin flora and in doing so indirectly reduce the inflammation. The inflammation may be directly treated using a corticosteroid cream or lotion to control the body’s immune response. Seborrheic dermatitis can be very persistent once it starts, so staying with treatment is required and preventative treatment is useful even when the symptoms are gone.

Published on March 1, 2010