Dandruff is a common scalp disorder that affects almost half of the population regardless of gender and ethnicity. Dandruff may be viewed as cosmetically unappealing and may also cause itching with greater severity during the winter season.
Dandruff vs. Seborrheic Dermatitis
Dandruff shows many of the same characteristics of seborrheic dermatitis, an inflammatory skin condition usually affecting the scalp. Both affect areas of the body with sebaceous glands which discharge oils and only differ in location and severity. Dandruff refers to itchy, flaking skin on the scalp without visible inflammation of the scalp, whereas seborrheic dermatitis affects the scalp, face, and upper chest (also involving flaking, scaling, inflammation, and itchiness, with possible redness).
While seborrheic dermatitis is a specific diagnosis, dandruff is a condition that can arise from several causes. While there are several known causes and triggers, the causes of dandruff are difficult to pinpoint.
Some of the possible causes and triggers to a flaky scalp are discussed below.
1) Normally Occurring Yeast on the Skin: Malassezia
Malassezia is yeast that is mainly found on the seborrheic regions (regions of the body with abundant oil glands). It is normally present on the scalp, but it is present in much greater numbers on those with dandruff and seborrheic dermatitis as compared to those without dandruff or seborrheic dermatitis. The greater amount of Malassezia correlates with seborrheic dermatitis severity.
In those with dandruff, there are abnormalities found in the skin cells (corneocytes) as well as the structures (desmosomes) that connect the skin cells together. Because of this, the skin cells do not form as well of a tight barrier that is responsible for maintaining moisture in the skin. There is itchiness from irritation due to the poor barrier and this scratching will elicit histamine release which causes even more itching. Apart from this, the fungus (Malassezia) produces enzymes that degrade oily secretions into other more inflammatory oils that cause further irritation and further breakdown of skin cells. This begins a vicious cycle. Although Malassezia exists normally in the human body, it can become harmful when it becomes out of balance in the case of seborrheic dermatitis. As harmful agents, they trigger the immune system which results in inflammation of the skin.
Treatment of dandruff often involves controlling the abundance of yeasts such as Malassezia.
2) Age: Infancy, Puberty, and in Older Adults
Seborrheic dermatitis seems to occur in three phases of life:
The first three months of life when sebaceous gland activity is temporarily high due to the effects of the lingering hormones from the mother after birth
During puberty when the sebaceous gland activity is high from the new surge of hormones
After the age of 50 and this is when sebaceous gland activity starts to decline
Researchers and doctors still do not understand why seborrheic dermatitis seems to occur at both times when sebaceous gland activity is high (birth and puberty) and when it reduces (after age 50).
3) Sun Exposure
Sun exposure is reported to trigger dandruff. Flakes around the scalp are found to be associated with too much sunlight exposure. However, sun exposure has also been seen to kill Malassezia[1,3] and the jury is still out on the role of sun exposure in otherwise healthy people.
On the other hand, those with conditions that make them sensitive to light (such as lupus) may develop scaling on the scalp after sun exposure.
4) Chemical-Based Irritation of the Scalp
Mild chronic irritation of the scalp may be the result of harsh daily routines such as hard brushing, over-shampooing, and certain hair products. An accumulation of these irritations may be responsible for dandruff. The stratum corneum is the outer layer of the epidermis that functions as a barrier against water loss and entry of harmful organisms. An impaired barrier in the scalp stratum corneum has been associated with increased dandruff occurrence. Frequent combing and over-shampooing are both known causes of scalp stratum corneum barrier impairment. Hair dyes may cause painful irritation of the scalp. It is possible that this irritation caused by hair dye may occur more easily on the damaged dry scalp.
5) A Suppressed Immune System
Seborrheic dermatitis is are associated with immune-suppression, especially in HIV/AIDs. In immunocompromised patients. It is thought that the Malassezia yeast may be overgrown in those with weaker immune systems. For example, seborrheic dermatitis is more common in those with a weakened immune system such as in HIV/AIDS or in those that are receiving chemotherapy drugs.[10,11]
6) Environmental Influences
Wintertime brings a time of cold outside air and indoor heating leading to hot dry conditions. This can lead to more dryness and irritation during the winter months. Additionally, the rate of oil secretion by the oil glands on the skin decreases during the winter months. The balance of cold and dry weather with decreased oil production may lead to more flaking on the scalp, especially in those that are predisposed to dry skin.
Treatments for a Scaling Scalp
Table 1 – Treatment Approaches to a Dry Scalp
Cause for Scalp Scaling
Antifungal shampoos; herbal oils
Hormone-induced oily scalp
(likely has yeast overgrowth as a result)
Antifungal shampoos and daily scalp cleaning is important
Sun protection such as use of hats
Chemical based Irritation
Decrease shampoo frequency and decrease use of irritating hair products
If scaling occurs after hair dye, seek evaluation for hair dye allergies
Weakened immune system
Hair oils such as coconut oil (but hair oils can worsen yeast overgrowth)
If the scaling of the scalp is severe or very inflammatory in the opinion of a healthcare provider, another strategy that may be employed is the use of topical steroids to reduce the inflammation. If you think you have scalp scaling, please seek an evaluation with a health care provider instead of diagnosing yourself.
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