<Things you should know> The correct knowledge about "dandruff" (1) Explanation of the causes and symptoms of "dandruff" What is dandruff? Types of dandruff The mechanism and causes of dandruff What is the difference between dandruff and seborrheic dermatitis? Dandruff is a natural physiological phenomenon that occurs in everyone who is healthy, but it can become a concern if it increases in quantity or becomes noticeable. Furthermore, dandruff can sometimes be caused by underlying medical conditions, so it's important to have accurate knowledge about it. This article, supervised by a dermatologist, explains the common causes and symptoms of dandruff. What is dandruff? First, let's confirm the definition of dandruff. What is dandruff? Dandruff refers to flakes of dead skin cells that have sloughed off the scalp. It's essentially old skin cells pushed out during the scalp's natural turnover process (skin regeneration). It's similar to dead skin cells and usually contains a mixture of sebum, sweat, and dust. Dandruff can occur in anyone who is healthy, but when it increases in quantity or size, it can become quite noticeable, with large flakes of dandruff falling onto the shoulders or clearly visible in the hair. This condition is called "dandruff syndrome." Types of dandruff Dandruff can be broadly divided into two types based on the proportion of sebum it contains: dry and flaky, and oily and greasy. Let's take a closer look at the characteristics of each. Dry dandruff (scaly flakes) This type of dandruff is common in dry scalps and consists of dry, flaky flakes. It is said to be more prevalent in people with dry skin. It can also be caused by using shampoos with strong cleansing power or washing too frequently, which can lead to a lack of essential oils on the scalp. Oily dandruff (greasy) Unlike dry dandruff, which flakes off easily, this type of dandruff sticks firmly to the roots of the hair. It is more likely to appear when the scalp produces excessive sebum due to factors such as an oily diet, insufficient washing, or hormonal imbalances. The mechanism and causes of dandruff How does dandruff develop? Let's look at the causes of dry dandruff and oily dandruff. How dandruff occurs The scalp is constantly undergoing a process of cell turnover. Epidermal cells are born in the basal layer, the lowest layer of the epidermis, and are pushed upwards until they reach the stratum corneum, where they eventually flake off as dandruff. This is how dandruff forms. Normally, dandruff is washed away during shampooing, but if the scalp's cell turnover is disrupted for some reason, dandruff can become larger, more noticeable, and increase in quantity, resulting in a condition known as dandruff. Main causes of dandruff Dandruff can occur in anyone, but it is believed that lifestyle habits are deeply related to the cause of noticeable and increased dandruff. For example, poor diet, irregular lifestyle, lack of sleep, stress, and fatigue are among the causes. These lifestyle habits can lead to hormonal imbalances, which can affect the turnover of the scalp and lead to the development of dandruff. In addition to the causes mentioned above, there are also causes specific to dry dandruff and oily dandruff. Let's look at each type of dandruff. Main causes of dry dandruff When the scalp becomes dry, dry dandruff is more likely to occur. The following are some of the causes of a dry scalp: Washing your hair too much Using a shampoo with strong cleansing power Dry season UV damage Lack of moisture in the scalp due to aging Main causes of oily dandruff An oily scalp that produces dandruff indicates excessive sebum secretion. Of particular concern is a type of fungus called Malassezia. Although it is a fungus, it is a commensal bacterium that is present on everyone's skin, but it is known to proliferate by feeding on sebum. Malassezia breaks down sebum, increasing free fatty acids, which accelerates scalp cell turnover and increases the amount of dandruff. In addition, the following are thought to be contributing factors to an increase in oily dandruff: Dirt residue after washing hair Shampoo residue Sleeping with hair products like wax in your hair I sweat a lot My head gets sweaty when I wear a hat or helmet. What is the difference between dandruff and seborrheic dermatitis? Seborrheic dermatitis can cause excessive dandruff. So, how does it differ from dandruff? Let's look at the definition of seborrheic dermatitis along with this distinction. What is seborrheic dermatitis? This condition appears in areas with active sebum secretion, such as the face, head, armpits, and genitals. Red rashes are seen on dry, flaky skin. When it occurs on the scalp, there is a lot of dandruff and the scalp becomes red. Infant-type seborrheic dermatitis usually resolves on its own, but adult-type seborrheic dermatitis can persist or recur repeatedly. The difference between dandruff and seborrheic dermatitis Dandruff is a physiological phenomenon, and dandruff refers to a condition where dandruff is noticeably abundant. However, seborrheic dermatitis is a pathological stage. In seborrheic dermatitis, dandruff is part of the symptoms, and treatment may involve lifestyle changes and, if necessary, the use of topical steroids or other medications. In both cases, a major contributing factor has been identified as being related to Malassezia fungus. If dandruff persists or if you experience other symptoms besides dandruff, you may have developed a condition such as seborrheic dermatitis, so you should see a dermatologist as soon as possible. Other major diseases that cause dandruff besides seborrheic dermatitis Dandruff can be a symptom of conditions other than seborrheic dermatitis. The main ones are as follows: Psoriasis vulgaris While dandruff can be seen in psoriasis vulgaris, the symptoms are not limited to the scalp. It is a disease primarily characterized by inflammation and keratinization, resulting in skin that is red and covered with layers of silvery-white keratin. In the early stages, it is very difficult to distinguish from seborrheic dermatitis. Atopic dermatitis (adolescence and adulthood) Dandruff can also be seen on the scalp in people with atopic dermatitis. The mechanism of atopic dermatitis is not yet fully understood, but it is thought that external stimuli, in addition to factors such as the skin's barrier function not working properly and individual constitution, are contributing factors.External factors include dust mites, house dust, skin flora, mental stress, and humidity. In particular, mental stress is considered a significant contributing factor to the worsening of atopic dermatitis in adolescents and adults. Tinea capitis (ringworm of the scalp) Recently, there has been an increase in cases of infection among athletes, particularly those in judo. When infected, symptoms include hair loss in an oval pattern, rashes, and sometimes dandruff-like flakes. Supervised by: Dr. Yuki Horiuchi, Director of Akihabara Skin ClinicAfter graduating from the Faculty of Medicine at Tokyo Women's Medical University, she worked at dermatology and cosmetic clinics in Tokyo before opening Akihabara Skin Clinic in 2007. She is a certified specialist of the Japanese Dermatological Association, a director of the Japanese Society for Medical Hair Removal, and an advisor to the A-Care Association. She is a member of the Japanese Dermatological Association, the Japanese Society for Aesthetic Dermatology, the Japanese Society for Laser Medicine, and the Japanese Society for Anti-Aging Medicine, among others. We take care to post accurate information,Please point out any incorrect information. 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