Hair, skin & creams · cat safety
Is 5-FU (fluorouracil) skin cream toxic to cats?
Deadly
No — 5-FU (fluorouracil) skin cream is one of the most poisonous creams in any home. Licking treated skin or biting the tube can cause severe vomiting, seizures and bone-marrow damage; it often kills dogs, and vets expect cats to be as sensitive. Go to a vet now.
Why deadly: Kills many dogs that swallow it; vets warn cats are very sensitive too — even a few licks may be life-threatening.
- Name
- 5-fluorouracil (5-FU) skin creamalso 5-FU, Fluorouracil cream, Flonida, Efudex, Prescription cream for skin cancer and sun-damaged skin
What counts
5-FU creams and solutions (1% / 5%), the tube, the applicator and the treated skin.
What's in it
Fluorouracil, a cancer drug that kills fast-dividing cells — in the gut lining, the bone marrow and the nervous system.
Brands it hides in
- Flonida cream — or any tube that says fluorouracil or 5-FU
- A small prescription tube from a dermatologist
- Treated patches of skin on the face, scalp or hands
Symptoms to watch for
- Severe vomiting, sometimes with blood
- Bloody diarrhoea
- Tremors, wobbliness
- Seizures that are hard to control
- Later: infections and bleeding (bone-marrow damage)
Fast — within 30 minutes to 6 hours (Pet Poison Helpline). Bone-marrow damage can appear up to 2 weeks later (Merck).
What to do — now
Go to a vet now — this is an emergency even if your cat looks fine.
- Take the tube.
- Don't make your cat vomit at home unless a vet tells you to.
- At home: keep the tube in a closed cupboard and keep your cat away from the treated skin — ask your doctor whether to cover it.
Where Indian cats meet it
Dermatologists in India prescribe 5-FU cream for sun-damaged skin and some skin cancers; the risk is a cat licking the treated skin or chewing a tube left on the dressing table.
Myth or fact
Myth“It's just a skin cream — a lick won't matter”
FactPet Poison Helpline calls topical 5-FU one of the most dangerous pet toxins: 'small amounts – even a lick for some pets – are highly toxic' (Pet Poison Helpline).
Sources
- Pet Poison Helpline: 5-fluorouracil (5-FU)
- US FDA: Fluorouracil products used on people's skin can cause serious reactions in pets
- Pet Poison Helpline (Brutlag): Topical toxic titans (PDF)
Facts last checked
General information for cat parents, not a diagnosis or a treatment plan. The facts come from ASPCA, Pet Poison Helpline, International Cat Care, the Merck Veterinary Manual and the other sources listed on every page — and we say so when the evidence comes from dogs or people. If your cat may have eaten something harmful, call your vet.