Dandruff, characterised by an itchy, flaking scalp, is a common condition affecting approximately half of the world's population. It is considered the mildest form of seborrheic dermatitis, a type of skin inflammation that typically impacts the head, face, or trunk.
Experts do not yet fully understand the exact causes of dandruff, but various factors are likely to contribute. A yeast called Malassezia, which normally lives harmlessly on the scalp, is a leading suspect, with its overgrowth linked to scalp inflammation.
For occasional light flaking without significant redness or itch, over-the-counter dandruff shampoos can be effective. Common active ingredients include zinc pyrithione, selenium sulfide, and ketoconazole, which help reduce Malassezia populations and inflammation.
These shampoos should be massaged into the scalp and left for a few minutes before rinsing, used three times a week. If symptoms clear, usage can often be reduced to once a week. If a shampoo becomes ineffective, switching to a different active ingredient temporarily may help.
It is advisable to consult a doctor if flaking returns quickly after stopping medicated shampoo, if thick, red plaques with silvery-white scales appear, or if hair loss or a burning/stinging sensation accompanies flakes. These symptoms may indicate other conditions like psoriasis or scarring alopecia.