Treating dandruff well is a four-week project with a lifetime maintenance tail. Here is the complete playbook, from first flake to long-term control.

Step 1: Start the right shampoo (week 1)

Pick one proven antifungal: ketoconazole 2%, zinc pyrithione, or selenium sulfide
Use 2-3 times a week; on other days use a mild regular shampoo or just rinse
Massage into the scalp, leave 3-5 minutes, rinse fully
Thick scale buildup? Add a salicylic acid shampoo once a week to lift it

Step 2: Judge honestly (weeks 2-4)

Expect visible improvement in 2-4 weeks - less itch first, then fewer flakes
No change after 4 weeks of correct use: rotate to a different active ingredient
Still nothing, or redness spreading: dermatologist - this is where seborrheic dermatitis or psoriasis gets diagnosed