Cat losing hair: the test to do before you start worrying

The question behind the question

A cat loses hair all year round. The real question is not how much hair is on the sofa, it is whether the hair is falling out or whether the cat is pulling it out.

That distinction decides everything, and it is made at home with no equipment. Run your hand against the lie of the coat over a thin area, then look at the skin and at the hairs that are left.

If the hairs have a blunt end, as though cut straight across, the cat is breaking them off by licking. A cat's tongue is a rasp: it is covered in keratinised hooks that take hair off flush. Plenty of owners swear their cat does not lick, because a cat licks at night and hides to do it.

If the hairs are growing back to a fine point and the skin shows crusting, redness or raw areas, the loss is something other than over-grooming.

What causes genuine hair loss

Fleas come a long way ahead. Not because they are dirty, because they bite. A cat allergic to flea saliva goes thin over the lower back, the base of the tail and the backs of the thighs, and a single bite is enough to set off the reaction. Indoor cats are not exempt: fleas come in on clothes. The area affected is itself a clue, because it matches where the flea prefers to sit.

Food and environmental allergies come next. They tend to affect the head, the neck and the belly.

Skin parasites, ringworm among them, give round patches that spread. Ringworm passes to people, and it is particularly common in kittens and in cats coming from a rescue or a breeder.

Internal disease changes the coat before it changes anything else. Hyperthyroidism, diabetes and kidney disease all leave the coat dull, brittle and sparse. In a cat over seven that is going thin without scratching, the hormonal line of enquiry deserves a blood test.

Finally, a cat that licks down to the skin with no lesion and no parasite can be stressed. That is a diagnosis reached last, once the rest has been ruled out, never first. A house move, a new animal, a litter tray that has been shifted are all enough.

What is of no use

Changing food at random, with no test plan, proves nothing and loses weeks. A serious food elimination trial runs at least six to eight weeks on a single food, with no treats, and finishes with a reintroduction to confirm.

Oil-based supplements do not repair a coat damaged by hormonal disease or by fleas. They help a healthy coat stay healthy, which is a different story.

A soothing shampoo eases sore skin. It treats neither fleas nor an allergy.

My cat lives indoors, are fleas really possible?

Yes. Fleas come in on clothes and shoes. An allergy to flea saliva is triggered by a single bite, and it typically affects the lower back, the base of the tail and the backs of the thighs.

Could changing food fix the problem?

Not at random. A serious food elimination trial runs six to eight weeks on a single food, with no treats at all, and finishes with a reintroduction to confirm. Switching brands at random loses weeks and proves nothing.

Can stress explain hair loss?

Yes, but it is a diagnosis reached last, after parasites, allergies and hormonal disease have been ruled out. Never first.