While some of these disorders are infections, allergic reactions or immune responses all involve some degree of inflammation (see What is Inflammation?). Some are conditions confined to the scalp (e.g., tinea capitis, also called ringworm), some are scalp manifestations of a more general or systemic condition (e.g., psoriasis).While each condition has specific symptoms, the presentation of symptoms may be very similar from one condition and another. For example, seborrheic dermatitis of the scalp and psoriasis of the scalp have a number of symptoms and clinical features in common. Some conditions, or milder forms of conditions, can be managed by home care with over-the-counter medications. A dermatologist or other physician should treat more severe or systemic conditions such as psoriasis. (see Diseases and Disorders of the Scalp).
What Is Inflammation?
Inflammation is one of the body's principal defense systems against invasion by micro-organisms or injury by thermal, chemical or physical trauma. The reason for inflammation is to help in healing an affected area; a simple example is inflammatory response to a splinter in the finger, resulting in expulsion of the splinter and healing of the wound.
When the immune system detects an invasion or injury, a cascade of inflammatory precursors is set into motion. When the reason for the inflammatory response is resolved, the inflammatory response is concluded under control of the immune system. The inflammatory response can go awry, however, to the point that inflammation becomes the disease instead of part of the healing process. For example:
- Inflammatory response to a local bacterial infection spirals out of control, becoming a body-wide inflammation of all major organs that ends in critical illness or even death.
- Inflammation in response to local insult proceeds to a persistent, chronic inflammatory state that may be associated with arthritis, heart disease, complications of psoriasis and a number of other chronic conditions.
How and why regulation of the inflammatory response sometimes fails is a subject of intense ongoing medical investigation.
Various types of bacteria, some that live normally and harmlessly on the skin, can become invasive and cause infection. Staphylococci ("staph") are frequent offenders; when they infect the scalp the result is often folliculitis (inflammation of hair follicles), with or without abscess formation. Skin is inflamed and painful around the infected follicles. Persistent folliculitis can lead to permanent hair loss. Treatment with antibiotics is usually necessary.
Viral scalp infection may be due to herpes simplex (the "cold sore" virus) or herpes zoster (the "shingles" virus). Symptoms may include folliculitis. Herpes zoster infection produces inflamed and extremely painful lesions on the skin-a classic symptom of shingles. Anti-viral medication may be prescribed after appropriate diagnosis.
Diseases and Disorders of the Scalp