Brown stains under a cat's eye: porphyrins were never actually found
Published by Planète Pets · managing editor: Clément Lacaille · how our guides are written
Look up why the fur browns under a Persian's eye and the same answer comes back everywhere: porphyrins, pigments carried in tears that supposedly oxidise on contact with air. It is the selling point of "anti-porphyrin" wipes. One study went looking for those pigments — and found none. Our eye care guidance is gathered in the cat care and grooming section.
Contents · 4 sections
A pigment hunt that came back empty
Newkirk, Hendrix and Keller published in 2011, in Veterinary Ophthalmology, a study searching for porphyrins in feline ocular tissues (see the study). The authors used spectrofluorometry on the lacrimal glands, the third eyelid gland and the corneas of 14 healthy cats, plus 18 corneal sequestra. No porphyrin was detected above background, while the positive control — a hamster Harderian gland, rich in porphyrins — and the laboratory standards clearly contained them. Their conclusion is unambiguous: porphyrins are not the source of the brown colour in cats.
One honest limit must be stated: they assayed tissues, not the tear film itself nor the stained fur. So the study invalidates the explanation as it is served everywhere, without formally establishing what does colour the hair. In other words, the correct answer today is "we do not know", not "it is something else".
What is established, on the other hand: conformation
Sieslack, Farke, Failing, Kramer and Schmidt published in 2021, in PLOS ONE, a CT study of 69 Persians and 10 European cats. Twenty-one of the 69 Persians, about 30 %, showed bilateral tear staining, and those cats had significantly higher skull indices than the others (cephalic index 90.5 versus 79.2; p = 0.0049). Staining is therefore correlated with the degree of facial flattening — a result already used in our article on tear staining in the exotic shorthair, which details the path of the tear duct.
What this changes about daily care
- No product targeting porphyrins has a measured basis in cats: the pigment it claims to dissolve was not found.
- Cleaning still matters, to prevent damp fur from macerating rather than to "remove a pigment" — our guide to daily brushing of a Persian describes the routine.
- A dry, localised brown mark on the cornea is not a tear stain: it is a lesion to have examined, as explained in our article on corneal sequestrum.
Frequently asked questions
Do porphyrins exist in dogs, then?
That question falls outside this study, which covers feline tissues only. Nothing licenses extending or denying the result for another species.
Can tear stains be removed for good?
When they stem from skull conformation, no. Maceration can be limited; the cause cannot be removed.
Is chronic tearing worth a consultation?
Yes, at least once, to rule out a treatable cause — ulcer, entropion, infection — before putting it down to a breed trait. Find all our guides on the cat hub.
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This guide is part of Planète Pets’s Cats universe. Our advice is general in nature: for any health concern, your veterinarian remains the only reference.
