The underlying condition, scalp ringworm, is a usually harmless fungal infection of the scalp and hair that occurs as scaly spots and patches of broken hair on the head. Ringworm of the scalp is most commonly seen in children. Though several different species of fungus may cause scalp ringworm, they are generally known as dermatophytes. Scalp ringworm may be acquired by direct contact with infected people or with contaminated objects that have been handled by infected people (such as combs, pillows, and sofas). Most commonly, scalp ringworm infections are caused by dermatophytes that prefer to grow on humans. Less commonly, the fungus may be spread from infected animals (zoophilic dermatophytes) or from the soil (geophilic dermatophytes).
Kerions usually occur in people who have been infected with zoophilic dermatophytes. A kerion is believed to be an overly active response of the immune system or an allergic reaction to the fungus.
A kerion is seen almost exclusively in children, but, on rare occasions, it may be seen in teens and young adults.
Fever and pain may accompany the kerion. In addition, the lymph nodes at the back of the scalp, behind the ears, or along the sides of the neck may be swollen.
Sometimes the doctor will also perform a fungal culture in order to document the presence of fungus or to discover the particular organism that is causing the kerion. The procedure involves:
- Plucking a few hairs or piercing any pus-filled lesions in the involved areas of the scalp
- Rubbing a sterile cotton-tipped applicator across the skin to collect scale and pus
- Sending the specimen away to a laboratory
Occasionally, a Wood's lamp is used to look for the fungus. In this procedure, the doctor shines a black light at the scalp, and certain strains of dermatophytes may appear as yellow-green fluorescent spots when seen under this light.
A kerion is treated with oral antifungal medicines because the fungus grows deep into the hair follicle where topical creams and lotions cannot penetrate. Scalp ringworm and kerion usually require at least 6–8 weeks of treatment with oral antifungal pills or syrup, including:
- Selenium sulfide shampoo
- Ketoconazole shampoo
If the kerion is particularly tender and painful, your child's doctor may recommend starting oral corticosteroids (cortisone pills or syrup). Steroids are strong medications that can quickly reduce the inflammation present in the kerion.