Many of the symptoms, causes, and treatment of dandruff can be found in our seborrheic dermatitis article which we encourage you to review. It is more comprehensive than this abbreviated article. Some of the information is also repeated as these conditions overlap each other. However, for those of you that are interested specifically in the mildest form of seborrheic dermatitis which is typically considered to be dandruff, this article is for you.
Dandruff is one of the most common skin conditions in humans and is thought to affect around 50% of the population during their lifetime. The condition is the mildest clinical presentation of seborrheic dermatitis which is a rash that affects mainly the scalp and face. There is also an extremely severe presentation of seborrheic dermatitis with is a total body red, scaly, flaky rash called erythroderma. Thankfully, this condition is extremely rare and common dandruff is not thought to progress to this severe condition. Some also consider dandruff to be a form of facial and scalp eczema.
The most common symptom of dandruff is a dry, flaky, itching, scaly scalp. It also sometimes affects the facial skin including the nasolabial folds (the lines between the nose and the outside of the lips), sides of the nose, eyebrows, beard area, and face. If the rash involves other areas outside of just the scalp, then the condition would probably be considered seborrheic dermatitis. The rash is may be itchy, painful, or embarrassing since many of the flakes appear on the facial skin or on the shoulders when wearing darker clothing.
There are not very many studies investigating the causes of dandruff specifically and it is usually lumped together with seborrheic dermatitis. The causes of seborrheic dermatitis and dandruff are “multifactorial” which means multiple factors (both genetic and environmental) are suspected to trigger the disease. Many individuals that suffer from dandruff or seborrheic dermatitis have a family history of the condition. More recently, genes that play a role in the immune system or a change in the way the skin naturally grows has been implicated.1 Environmental factors also play a critical role in the condition. A normal harmless yeast lives on our skin throughout our lives without causing problems. In seborrheic dermatitis, the yeast overgrow by feeding on natural body oils. The specific oil produced by people with seborrheic dermatitis is slightly different resulting in lower amounts of healthy anti-inflammatory skin oils, changes in the amount of different healthy bacteria, and an imbalance of the normal skin bacteria.2 The yeast also produces a protein (enzyme) called lipase which turns healthy body oils into inflammatory irritating oils in people predisposed to seborrheic dermatitis.2
Because the condition is so common in the general population, several over-the-counter shampoos are available which improve the skin. They will not cure the disease but usually control it to an acceptable level. Most of the products contain active ingredients targeted at either reducing the amount of yeast on the skin, reducing the scaling of the scalp by dissolving the flakes, or creating an anti-inflammatory effect on the skin. The active ingredients include pyrithione zinc, coal tar, selenium sulfide, ketoconazole, salicylic acid, or sulfur. Prescription steroids available from a doctor are available and can be used periodically to improve the itching, flaking, and scaling of the scalp.