Why Dandruff Keeps Coming Back, Even When Your Shampoo Works
By AntherShare
5 min read · Reviewed October 2026
The short answer
- Anti-dandruff shampoos keep the yeast behind dandruff in check. They don't remove it.
- Stop the shampoo and the yeast grows back. In a 575-person trial, 47% of people on a placebo shampoo had dandruff again within six months.
- People who kept using the medicated shampoo once a week after clearing: 19%.
What causes dandruff?
Not dry skin. Three things act together: the oil your scalp makes, a yeast called Malassezia that feeds on it, and how your skin reacts to what the yeast leaves behind.
The yeast, mainly M. restricta and M. globosa, breaks scalp oil down into fatty acids that irritate sensitive skin. The skin then sheds faster and unevenly, and those clumps are the flakes (Ro & Dawson, 2005).
You can lower the yeast and the oil. You can't change how your skin reacts. That's why dandruff is managed, not cured once.
Why does dandruff come back when I stop?
Because the shampoo was holding the yeast down. In a 1995 trial, 575 people with moderate to severe dandruff used 2% ketoconazole shampoo twice a week, and 88% cleared well. The 312 who cleared were followed for six months:
Share whose dandruff came back within 6 months. Peter & Richarz-Barthauer, 1995.
Weekly use cut relapse to less than half the placebo rate. But one in five still relapsed, so maintenance lowers the odds; it doesn't guarantee anything. This trial tested ketoconazole. Most other antifungal trials ran for only about four weeks, so the long-term picture for them is less known (Okokon et al., 2015).
"My shampoo worked, then stopped." Why?
I couldn't find good clinical evidence that people become resistant to anti-dandruff shampoos through normal use. The usual reasons are simpler:
- You use it less once the flakes clear. That's the relapse pattern above.
- It's rinsed off too fast. Ketoconazole's UK prescribing information says to leave it on for 3–5 minutes. The American Academy of Dermatology says some shampoos need 5–10.
- It's going on your hair, not your scalp. The yeast lives on scalp skin.
- It isn't dandruff. See the warning signs further down.
Still not working after fixing these? The AAD suggests switching to a shampoo with a different active ingredient.
Which active ingredient should I look for?
Most of these can't be ranked against each other, because many comparisons rest on a single study. Using a proven one properly, and not stopping early, matters more than which one you pick.
Want the head-to-head numbers? Read piroctone olamine vs ketoconazole vs climbazole.
Does shampoo pH matter?
For salicylic acid, a lot. It's a weak acid (pKa 2.97), and only its un-ionised form moves easily into skin. How much of it is un-ionised depends on the shampoo's pH:
Share of salicylic acid in the un-ionised form. Calculated with the Henderson–Hasselbalch equation.
At pH 4.7, a salicylic acid shampoo has about 20 times more of the useful form than at pH 6, but it's still under 2%. Lower pH helps a lot; it doesn't make salicylic acid "fully active". Most labels don't state pH, so if a brand leans on salicylic acid, ask them what pH the formula runs at.
How do I keep dandruff away?
If you oil your hair, wash it out with your anti-dandruff shampoo. I haven't found good evidence either way on whether oiling makes dandruff worse, and none that it treats dandruff.
See a dermatologist if
- There's red, greasy scale on your eyebrows, the sides of your nose or behind your ears. That can be seborrhoeic dermatitis.
- You have thick, silvery, sharply edged patches, often past the hairline. That can be psoriasis.
- Itching and redness started with a new product.
- There's patchy hair loss with scaling, especially in a child.
- A month of correct use hasn't helped.
Where Anther fits
Scalp Reset uses piroctone olamine and climbazole, plus salicylic acid. We haven't run a clinical trial on our own formula, so the relapse numbers on this page are for ketoconazole, not our bottle. The same rule applies to ours: once the flakes clear, keep using it weekly.
See Scalp Reset →Quick questions
Can dandruff be cured permanently?
Not with a shampoo. The yeast involved lives on everyone's scalp, and no shampoo removes it for good. Dandruff can be kept under control with regular maintenance use.
How often should I use anti-dandruff shampoo?
About twice a week for two to four weeks to clear flakes, then about once a week to keep them away. Your product's label overrides this.
Why did my anti-dandruff shampoo stop working?
Usually because you're using it less often than when it worked, it isn't left on the scalp for a few minutes, or the problem isn't dandruff. There's no good clinical evidence that people become resistant to these shampoos through normal use.
Is dandruff caused by a dry scalp?
No. Dandruff is linked to scalp oil and yeast, not dryness. A tight, dry scalp with fine flakes and no oiliness may be dry skin instead, which needs a gentler routine, not an antifungal.
Written by Hemanth Kumar, founder, Anther. Found an error? Tell us and we'll correct it here.
References (6)
- Ro BI, Dawson TL. The role of sebaceous gland activity and scalp microfloral metabolism in the etiology of seborrheic dermatitis and dandruff. J Investig Dermatol Symp Proc. 2005;10(3):194–7. doi:10.1111/j.1087-0024.2005.10104.x
- Peter RU, Richarz-Barthauer U. Successful treatment and prophylaxis of scalp seborrhoeic dermatitis and dandruff with 2% ketoconazole shampoo: results of a multicentre, double-blind, placebo-controlled trial. Br J Dermatol. 1995;132(3):441–5. PubMed 7718463
- Okokon EO, Verbeek JH, Ruotsalainen JH, Ojo OA, Bakhoya VN. Topical antifungals for seborrhoeic dermatitis. Cochrane Database of Systematic Reviews. 2015. Cochrane CD008138
- Ketoconazole 2% w/w shampoo: Summary of Product Characteristics (posology). electronic medicines compendium (UK)
- American Academy of Dermatology. How to treat dandruff. aad.org
- Salicylic acid: pKa 2.97 at 25 °C. reference value; un-ionised share = 1 / (1 + 10(pH − pKa)).