Wikipedia has a good definition. Dandruff is due to the excessive shedding of dead skin cells from the scalp. Dandruff can also be caused by frequent exposure to extreme heat and cold. As it is normal for skin cells to die and flake off, a small amount of flaking is normal and in fact quite common.
Some people, however, either chronically or as a result of certain triggers, experience an unusually large amount of flaking, which can also be accompanied by redness and irritation. Most cases of dandruff can be easily treated with specialized shampoos.
Those affected by dandruff find that it can cause social or self-esteem problems. Treatment may be important for both physiological and psychological reasons.
According to the Mayo Clinic, “Dandruff is a common chronic scalp condition, which is marked by itching and flaking of the skin on your scalp. Although dandruff isn’t contagious and is rarely serious, it can be embarrassing and sometimes difficult to treat.”
What causes dandruff?
According to Wikipedia “As the epidermal layer continually replaces itself, cells are pushed outward where they eventually die and flake off. In most people, these flakes of skin are too small to be visible.
However, certain conditions cause cell turnover to be unusually rapid, especially in the scalp. For people with dandruff, skin cells may mature and be shed in 2–7 days, as opposed to around a month in people without dandruff. The result is that dead skin cells are shed in large, oily clumps, which appear as white or grayish patches on the scalp, skin and clothes.
Dandruff has been shown to be the result of three required factors.
- Skin oil commonly referred to as sebum or sebaceous secretions.
- The metabolic by-products of skin micro-organisms (most specifically Malassezia yeasts.
- Individual susceptibility
Common older literature cites the fungus Malassezia furfur (previously known as Pityrosporum ovale) as the cause of dandruff. While this fungus is found naturally on the skin surface of both healthy people and those with dandruff, it was later discovered that a scalp specific fungus, Malassezia globosa, is the responsible agent.
This fungus metabolizes triglyrides present in sebum by the expression of lipase, resulting in a lipid byproduct oleic acid (OA). Penetration by OA of the top layer of the epidermis, the stratum corneum, results in an inflammatory response in susceptible persons which disturbs homeostasis and results in erratic cleavage of stratum corneum cells.
Rarely, dandruff can be a manifestation of an allergic reaction to chemicals in hair gels/sprays/shampoos, hair oils, or sometimes even dandruff medications like ketoconazole.
There is some evidence that food (especially sugar and yeast), excessive perspiration, and climate have significant roles in the pathogenesis of dandruff.
You can treat flaking and dryness with over-the-counter dandruff or medicated shampoos. Shampoo the hair vigorously and frequently (preferably daily). Loosen scales with the fingers, scrub for at least 5 minutes, and rinse thoroughly. Active ingredients in these shampoos include salicylic acid, coal tar, zinc, resorcin, ketoconazole, or selenium.
Shampoos or lotions containing selenium, ketoconazole, or corticosteroids may be prescribed for severe cases. To apply shampoos, part the hair into small sections, apply to a small area at a time, and massage into the skin. If on face or chest, apply medicated lotion twice per day.
When to contact a doctor
Call for an appointment with your health care provider if seborrheic dermatitis symptoms do not respond to self-care or over-the-counter treatments.
Also call if patches of seborrheic dermatitis drain fluid or pus, form crusts, or become very red or painful.
Online medical resources
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