There is a greasy mark on my aniline leather sofa. Can I use a leather cleaner on it?

Why the usual answer works

Body oil from hands, hair and scalp is the soil an armrest and a headrest actually collect, and a detergent is the thing that lifts oil off a surface. On finished leather that reasoning holds well enough to be worth qualifying rather than refusing.

Usually recommended: Detergent.

Why it must not be used here

Aniline leather is not finished leather. The trade body describes it as porous and DYED rather than coated, and states plainly that cleaning agents will immediately darken nude leather. There is no surface film between the cleaner and the hide, so the liquid goes in rather than sitting on top, and the darkening is absorption into the leather rather than a residue that can be wiped back off. The trade body's prohibition list for finished leather is about protecting a water-based FINISH; aniline has no finish to protect, which makes it more vulnerable rather than less.

This damage cannot be undone by cleaning. There is nothing left on the surface to remove.

More about aniline leather and oil and grease on textile.

What to do instead

Go dry, and go first. The trade body's own procedure for oil or grease on leather starts with cornstarch placed over the mark and rubbed gently with a finger until it coagulates with the oil, repeated as necessary — the absorbent lifts what it can before anything wet is introduced, and on a porous hide that is the only step that carries no darkening risk at all. Where the mark persists after that, the honest position is that the solvent step given for FINISHED leather does not extend to aniline, and that an unfinished dyed hide is the case the trade calls difficult. Treat a visible test in a hidden place as compulsory rather than advisable, and a valued piece as a job for a leather specialist. Finished leather and this material are not interchangeable: what is safe on one is not safe on the other, so identify which you have before touching it.

• Absorbent powder treatment — Lifting an oily mark out of a porous surface with a powder rather than dissolving it with a liquid. The gentlest route on anything water would ruin.
• Dry soil removal — Taking the loose material away before any liquid touches it. Skipped almost universally, and it is the step that decides whether the rest works.

This is a case where a specialist is a reasonable answer. Restoring a surface is a different trade from cleaning it, and continuing to try cleaning products on damage generally makes the eventual restoration harder.

The chemistry behind both halves

• Capillary absorption — Liquid moves through a porous material on its own, and it moves outward. It is why a stain grows after you treat it, and why a powder can pull one back out.
• Dye migration and colour bleeding — The colour of the thing you are cleaning can move too. Every trade body that publishes a stain procedure opens by telling you to test for it.
• Material compatibility — The reason a useful answer is about the surface rather than about the product. The same agent is the right answer and the wrong answer depending on what it lands on.