For years, the cosmetics industry has been convincing us that we need one bottle for the face and another for the body. Dermatologist Carlos Morales-Raya now says something you won't hear in the ads: washing your face with shower gel or a bar of soap "doesn't have to be a mistake".

The condition is simple. If the product is gentle, has a suitable pH and doesn't damage the skin's protective barrier, it can be used without a problem. Still, in his practice he usually recommends a dedicated facial cleanser, because "the skin on the face doesn't behave like the skin on the rest of the body".

A face that "squeaks" isn't cleaner

Chemist Arturo Álvarez-Bautista, director of the Spanish brand Arturo Alba, explains where the trap lies. Classic soap is alkaline and can strip away too many protective lipids, leading to dryness, tightness and irritation. A face that "squeaks" after washing, he says, isn't cleaner - it's signalling that it needs better conditions. But not every bar is soap, and not every shower gel is harsh. A syndet bar or a mild product also intended for the face can do the job perfectly well.

The difference lies in the skin itself. The face has more sebaceous glands and more visible pores, especially on the forehead, nose and chin. Over the course of the day, sebum, sunscreen residue, make-up and everything else we've applied builds up there.

That's why specialists split it up. For oily, acne-prone skin - cleansers with salicylic acid, azelaic acid or alpha-hydroxy acids like glycolic, which control excess oil and renew the surface and pores. For dry or sensitive skin, or skin with a damaged barrier - very gentle cleansers with mild surfactants and ingredients that hydrate and repair.

"What matters is the formula, not whether the packaging says 'shower' or whether it comes as a bar," says Morales-Raya. It's a sentence worth remembering before your next shopping trip: read the ingredients on the back first, and only then the advertising on the front.