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Dandruff is a skin condition of the scalp. It can result in social or self-esteem problems. A more severe form of the condition, which includes inflammation of the skin, is known as seborrhoeic dermatitis. and the underlying mechanism involves the excessive growth of skin cells. Diagnosis is based on symptoms.
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There is no known cure for dandruff. Antifungal cream, such as ketoconazole, or the keratolytic agent salicylic acid may be used to try to improve the condition. In addition, people in all areas of the world are affected.
Signs and symptoms
The main symptoms of dandruff are an itchy scalp and flakiness. Red and greasy patches of skin and a tingly feeling on the skin are also symptoms.
Emerging research suggests a potential association between dandruff and hair loss, primarily through the involvement of the Malassezia fungus and the resultant inflammatory responses. A study published in PubMed investigated the presence of Pityrosporum ovale (now classified as Malassezia) in individuals experiencing hair shedding. The findings indicated that 89.92% of subjects with hair shedding were carriers of Malassezia, compared to only 9.52% in the control group, suggesting a significant correlation between Malassezia colonization and increased hair shedding.
Dandruff and dry scalp are often confused since they share many of the same symptoms, but their causes and treatment are different. Dry scalp is simply dry skin on the scalp and can usually be easily treated with a skin care regimen.
Causes
thumb|right|Dandruff with shed hair can be symptomatic of dry skin (shed skin scales and hairs on a dark wooden tabletop)
The cause is unclear but believed to involve a number of genetic and environmental 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 and allergy sensitivity.
Microorganisms
Older literature cites the fungus Malassezia furfur (previously known as Pityrosporum ovale) as the cause of dandruff. While this species does occur naturally on the skin surface of people both with and without dandruff, in 2007, it was discovered that the responsible agent is a scalp specific fungus, Malassezia globosa, that metabolizes triglycerides present in sebum by the expression of lipase, resulting in the lipid byproduct oleic acid. In individuals affected by dandruff, the levels of Malassezia are 1.5 to 2 times their normal level.
For a long time, studies on dandruff predominantly focused on fungi, particularly the Malassezia species, which are major fungi colonizing the human scalp and the dominant members of the cutaneous fungal microbiome. Of the 14 known cultured species of Malassezia, the most clinically significant species are M. restricta and M. globosa. These species have been reported to be associated with skin diseases, including dandruff, seborrheic dermatitis, pityriasis dermatitis, and atopic dermatitis.
However, another microorganism community composed of bacteria also inhabits the human scalp and includes facultative anaerobic bacteria, such as P. acnes, and aerobic bacteria, such as Staphylococcus.
Seasonal changes, stress, and immunosuppression seem to affect seborrheic dermatitis. The size and abundance of scales are heterogeneous from one site to another and over time. Parakeratotic cells often make up part of dandruff. Their numbers are related to the severity of the clinical manifestations, which may also be influenced by seborrhea. However, it is mostly sold as cream and its main use is for treating athlete's foot, jock itch, and ringworm.
Other than zinc pyrithione, the most common anti-dandruff actives (outside the US) and part of many cosmetic shampoos, are piroctone olamine and climbazole. Very recent anti-dandruff shampoos use a new ester technology, propanediol caprylate.
Despite not being a direct antifungal, oral isotretinoin is able to clear dandruff and seborrheic dermatitis due to its strong suppression of sebum production via induction of apoptosis in sebaceous glands, which destroys the living space of the fungus who rely on sebum rich regions to thrive, thus significantly reducing the population of M. furfur and consequently relieving dandruff and its associated symptoms. However, it is typically not used for this purpose alone due to its high potential for systemic adverse effects and the availability of safer alternative agents listed above, but it is sometimes used at lower doses to treat severe treatment resistant seborrheic dermatitis.
Exfoliating agents
Coal tar causes the skin to shed dead cells from the top layer and slows skin cell growth.
Salicylic acid is an approved anti-dandruff active as per the US FDA OTC drug monograph and also used in many cosmetic anti-dandruff shampoos globally.