Why does dandruff keep coming back?

Because it is a relapsing condition, not an infection

This is the whole answer, and it reframes the problem usefully. Most dandruff is chronic and relapsing rather than something you catch and cure.

Treatment settles a flare. A maintenance routine is what keeps it settled. Those are two different jobs and they need two different levels of effort.

The most common mistake

Stopping everything the moment the flaking clears.

It is entirely understandable — the problem visibly went away. But the flare ended while the underlying tendency stayed, and the routine that was suppressing it stopped at the same time. A few weeks later it is back, and it looks like the treatment failed.

It did not fail. It was discontinued.

Why the shampoo from the pharmacy stops working

Over-the-counter shampoos cover a general case. They often help briefly and then stop.

A doctor's version is different in a specific way: they identify which cause you actually have and prescribe an active ingredient, a strength and a frequency for it. Flaking, itching and an oily scalp are symptoms with several possible causes — seborrhoeic dermatitis, fungal overgrowth, psoriasis and simple dryness among them — and they do not respond to the same thing.

Rotating through shop shelves is effectively guessing which one you have.

What improvement looks like

• Itching often eases first, within the first week or two.
• Visible flaking usually takes a few weeks to settle.

Your doctor reviews the scalp and adjusts the routine rather than leaving you on the same regimen indefinitely, which is the other half of why a prescribed approach outperforms a fixed one.

Living with it well

Expect maintenance rather than cure, and expect the routine to be adjusted over time. Colouring and styling are usually fine once the scalp has settled, though during an active flare it is better to wait — your doctor will say when it is reasonable to resume.

When to get it looked at rather than manage it

If it is not responding, if the scalp is inflamed or sore rather than just flaking, or if you are also shedding noticeably. That last one is worth assessing on its own terms.

Full detail on the anti-dandruff treatment page; see also whether dandruff causes hair fall. Consultation ₹500, waived against treatment.