Dandruff is a common and often chronic (ongoing) condition that is characterized by excessive shedding of dead skin cells from the scalp (skin that covers the top portion of the head). The medical term for dandruff is pityriasis simplex capillitii. Dandruff flakes appear as dry, white or grayish, emerging as small patches on top of the head. The condition is not contagious.
Skin is composed of three layers: the epidermis, dermis and subcutaneous tissue. The outer protective layer of skin is the epidermis. The middle layer is the dermis, which contains blood vessels, glands and nerve endings. The bottom layer is the subcutaneous tissue, which contains fat, nerves and blood vessels.
The outermost layer of the skin, the epidermis renews itself about once a month. Dead cells are continuously moving from the deepest layer of the epidermis to the skin’s surface, where they die. Usually the scalp sheds these dead cells unobtrusively. When people have dandruff, skin cell turnover becomes unusually rapid and the excess dead scalp cells are more visible as flakes.
Dandruff differs from two other skin conditions, seborrheic dermatitis and psoriasis. Both conditions are more severe and may involve other areas of the body besides the scalp. In seborrheic dermatitis, inflammation and itching (pruritus) accompany the flaky scales. Psoriasis is an inflammatory skin disease that features thicker flakes that keep piling up atop the scalp. Dry skin and contact dermatitis (resulting from irritating hair products) may also cause excessive scaling of the skin.
Dandruff usually begins during puberty and is common throughout adolescence and young adulthood. Typically, it peaks around age 40. However, older adults may also experience it. For some people, dandruff can be a lifelong nuisance.
Generally, dandruff is uncommon in children younger than age 10. In children, the scaly flakes are more likely the result of a fungal infection called scalp ringworm (tinea capitis). Unlike dandruff, ringworm usually causes a red, inflamed scalp as well as hair loss.
Dandruff occurs as a result of an overproduction of skin cells in the scalp. However, the exact mechanism of this process is unknown. It appears to be associated with an overabundance of a common skin yeast called Malassezia, but the relationship between the yeast and the skin flaking is not well understood.
The yeast feeds on oils (sebum) in the scalp. For that reason, people with oily skin and hair are more prone to dandruff. Men are also more likely to experience dandruff. This may be because men have larger sebaceous glands (glands that produce sebum). Some researchers believe male hormones may also play a role in dandruff.
People who live in certain climates may experience seasonal flare-ups when the weather turns colder and the air becomes drier, with remission occurring in the summer months.
- Emotional stress
- Hormonal fluctuations (e.g., puberty)
- Infrequent hair washing
- Overuse of styling products (e.g., hair sprays, gels)
In addition, people with certain conditions may have an increased likelihood of developing dandruff.
- Seborrheic dermatitis
- Neurological conditions, such as Parkinson’s disease
- Medical conditions that stress the body, such as heart attack and stroke
- Conditions characterized by hormonal imbalances, such as polycystic ovarian syndrome
- Conditions that affect the immune system, including human immunodeficiency virus (HIV) infection
Dandruff is a common and often chronic (ongoing) scalp condition. It is characterized by excessive shedding of dead skin cells from the scalp.
For most people, the signs and symptoms of dandruff are obvious. They typically include:
- White or gray, oily-looking flakes on the scalp, hair and clothing
- Pruritus (itchiness)
In addition, excessive scratching may cause breaks in the skin that can increase the risk of secondary skin infection. For this reason, it is important to seek medical treatment promptly if excessive and persistent itchiness occurs.
Patients should also consult a physician (dermatologist) if symptoms are severe and accompanied by redness and inflammation of the scalp. This may indicate the presence of a related condition, such as seborrheic dermatitis.
In some cases, dandruff may be mistaken for head lice, which is an infestation of an insect in the hair. Many physicians believe that misidentification is common, particularly among school-aged children, and has led to an over-diagnosis of head lice. Nits (lice eggs) can be distinguished from dandruff because they are firmly attached to the hair and hard to remove. Dandruff, on the other hand, can easily be flicked off the hair. In addition, nits are tiny and yellowish-white or gray in color, while dandruff is larger and white.
Generally, dandruff can be self-diagnosed and does not require medical treatment. However, if symptoms are severe and the dandruff flakes are accompanied by redness and inflammation of the scalp, it may be a related condition such as seborrheic dermatitis. In such cases, a patient should seek the care of a physician (usually a dermatologist).
Sometimes dandruff diminishes on its own but it improves more rapidly with proper treatment. The main therapy for dandruff is diligent and consistent shampooing of the scalp and hair. Washing of the head is important to remove the loose scales so the underlying skin can be treated.
Typically, patients require an over-the-counter dandruff shampoo to treat dandruff. These shampoos usually contain one of five active ingredients that counteract the buildup of skin cells. These ingredients include:
- Zinc pyrithione. An antibacterial and antifungal agent that has been shown to reduce the yeast associated with dandruff and seborrheic dermatitis.
- Coal tar. A byproduct obtained from coal manufacturing that has been proven to help conditions including dandruff, seborrheic dermatitis and psoriasis by slowing skin cell turnover. However, coal tar can give blond or light hair an orange tint and may cause photosensitivity.
- Salicylic acid. This drying agent may help eliminate scales and hair oiliness, but it may leave an excessively dry scalp, which can lead to more flaking. To counter the dryness, the use of a conditioner after shampooing is recommended.
- Selenium sulfide. This agent helps prevent skin cell turnover and may also reduce the number of yeast cells. However, shampoos with selenium sulfide can discolor blond, gray or chemically colored hair. Patients should only use them as directed and should rinse thoroughly after shampooing.
- Ketoconazole. A broad spectrum antifungal agent. Ketoconazole shampoos are available over-the-counter as well as by prescription (in higher dosages).
Hair should be washed daily with dandruff shampoo until the scalp condition is controlled. The shampoo should then be used two or three times a week to prevent recurrence. Alternating between two types of dandruff shampoos may work when flare-ups occur. Patients should massage the shampoo into the scalp while using their fingers to loosen scales. The shampoo should be left on the scalp for at least five minutes to allow the ingredients to work. Patients should then thoroughly rinse the shampoo out of their hair. Some experts suggest lathering twice for best results. Individuals may have to experiment with different types of dandruff shampoo in order to find the most effective type.
If over-the-counter dandruff shampoos fail to improve the dandruff after two weeks of use, a patient should contact their dermatologist. The dermatologist may prescribe a prescription-strength dandruff shampoo or a steroid lotion for more aggressive treatment of the scalp condition.
There are no known ways to prevent dandruff. However, people can take steps to minimize the outbreaks and their effects. These include:
- Shampooing often. Daily shampooing can remove excess oil from the head and may help prevent dandruff.
- Avoiding or minimizing the use of hair styling products (e.g., hair sprays, gels, mousses, waxes). These products can build up on the hair and scalp, making them prone to oiliness.
- Eating a well-balanced, healthy diet. A healthy diet will reflect on the hair and skin. In addition, excessive consumption of sugar (e.g., sweets, candies) and yeast (e.g., breads, beer) may encourage the growth of the yeast that triggers dandruff.
- Learning to manage stress. Stress can affect health in general and may help trigger or worsen dandruff.
Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following dandruff-related questions:
- What may be causing my dandruff?
- Is my dandruff a cause for concern?
- What are my treatment options? How effective are they?
- When can I expect to see results from the dandruff shampoo?
- How long should I use the dandruff shampoo?
- Will the dandruff come back if I stop using the shampoo?
- Do I need to make any lifestyle or dietary changes to control my dandruff?
- Should I change the type of hair styling products I use?
- Should I wash my hair more or less often?
- Will the dandruff get worse at certain times of year or will it remain the same year-round?
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