Why do I get dandruff in winter?

Because winter stacks the deck against a scalp that already has the underlying condition. Most dandruff is mild seborrheic dermatitis - driven by Malassezia yeast living on scalp oil - and Mayo Clinic notes its flares track stress, fatigue, and change of season. Winter supplies the triggers: cold dry outdoor air and heated indoor air dehydrate the scalp, which sheds more visible flakes, and flaky skin reads worse against dark winter clothes. The fix is not washing less - buildup feeds the yeast - but medicating smarter: the American Academy of Dermatology's self-care guidance centers on anti-dandruff shampoos with proven actives - ketoconazole 1%, zinc pyrithione, selenium sulfide, or salicylic acid - used as often as your scalp needs, left on for a few minutes before rinsing, and rotated if one stops working. Winter-specific additions: shorter, less-scalding showers (hot water strips more oil), and do not let flakes pile up for days between washes. If a medicated shampoo used properly for a month changes nothing, or the scalp is red, thick-scaled, or spreading past the hairline - that is a dermatologist visit, because psoriasis and true seborrheic dermatitis need prescriptions, not another bottle.