They're completely different. Dandruff comes from a yeast that feeds on sebum. Psoriasis is an inflammatory disease: the skin renews itself six times too quickly and accumulates in thick, well-defined plaques, often red underneath.

What's genetic is the sensitivity of the follicle, not the timing. The earlier you act, the longer you can preserve the follicle. A miniaturized follicle can still respond; a follicle that has disappeared cannot. Everything hinges on this window of opportunity.

What you shouldn't do is rub: friction and scratching irritate already sensitive skin. But there are chemical scrubs that are gentler and more suitable.

Sebum production is hormonal: it cannot be "re-educated". Spacing out washings simply allows sebum to accumulate, along with the itching and flaking that come with it.

A pH that is too alkaline, above 7, opens the cuticles, weakens the hair fiber, and disrupts the skin's protective barrier. The scalp thrives at around pH 5: this is the ideal pH level to maintain.

It's a yeast, Malassezia , present in everyone, that feeds on sebum. It therefore thrives on an oily scalp. Moisturizing alone won't solve the problem; you have to address the underlying cause.

A shock, an operation, a difficult period: the follicles switch to a resting phase, and hair loss occurs two to three months later. That's why we almost never make the connection with the event.

The frequency depends on the scalp, not on a set rule. A scalp that produces a lot of sebum needs to be washed often. What matters is the gentleness of the shampoo and its pH level, not the number of washes.

On its own, it can't do much: it only stays on the head for two minutes before being rinsed out. As part of a complete routine—scrub, serum, and supplement—it prepares the skin and does its part. The problem isn't the product itself, it's using it alone.

On the lengths of your hair, yes: some oils really do limit protein loss from the hair fiber. On the scalp, be careful: the yeasts responsible for dandruff feed on oils. Oil the lengths, not the roots.

Hair grows from the root, not the tip. Cutting removes split ends and improves the appearance, giving the impression of thicker hair, but does not change the growth rate.

But not in the way you might think. It's not circulation: it's the mechanical traction on the tissue under the scalp that alters the activity of the follicle cells. The hair emerges thicker. Regularity is key, just a few minutes a day.