What is Dandruff?

Dandruff is the commonest scalp condition on earth - roughly half of all adults deal with it at some point. It is also one of the most misunderstood. Here is what it actually is, and just as importantly, what it is not.

What dandruff actually is

• A mild inflammatory reaction of the scalp driven by a yeast called Malassezia - a normal resident of everyone's scalp that, in some people, feeds on scalp oils and produces by-products that irritate the skin
• The irritation speeds up skin turnover, and the excess cells shed as the visible white or yellowish flakes
• In medical terms, dandruff is the mildest form of seborrheic dermatitis - same process, confined to the scalp, without much redness

What dandruff is NOT

• Not dirt or poor hygiene - though infrequent washing lets flakes and oil accumulate and look worse
• Not contagious - you cannot catch it from a comb, a pillow or a person
• Not dangerous - it does not damage hair roots or cause baldness (though aggressive scratching can break hair)
• Not simply "dry scalp" - dandruff usually comes with excess oil; true dry scalp is a different, smaller-flaked condition

Why some people and not others

Everyone carries Malassezia. Whether you flake depends on your skin's sensitivity to its by-products - genetics, oiliness, stress, weather and how often you wash all play in. It typically begins after puberty (when oil glands switch on) and often improves with age.

The bigger sibling to know

When redness, greasy yellow scales and itching spread to the eyebrows, sides of the nose, ears or chest, that is seborrheic dermatitis - the same condition in a louder form, and worth a dermatologist's eye.

One-line summary

Dandruff is a harmless, non-contagious inflammatory flaking of the scalp driven by a normal yeast and your skin's reaction to it - half the world has it, and it is very manageable once you treat the cause rather than the flakes.