Is 5-Fluorouracil Cream (5-FU) Toxic to Cats and Dogs?
5-fluorouracil cream is severely toxic to both cats and dogs — a single lick has killed dogs within hours. There is no antidote. Any exposure is a go-now emergency.
Potentially life-threatening — treat any exposure as an emergency.
Potentially life-threatening — treat any exposure as an emergency.
In an emergency, do not wait.
Medical disclaimer: This tool is for general information only and isnot a substitute for veterinary diagnosis or treatment. Toxicity depends on the amount, your pet’s size, and health history. If your pet may have ingested something harmful, contact your veterinarian or a poison control hotline ((888) 426-4435 / (855) 764-7661) immediately — do not wait for symptoms to appear.
What is 5-Fluorouracil Cream (5-FU)?
5-fluorouracil cream is severely toxic to both cats and dogs — a single lick has killed dogs within hours. There is no antidote. Any exposure is a go-now emergency.
Also known as: fluorouracil, 5-fu, efudex, efudix, carac, tolak, fluoroplex, skin cancer cream, chemo cream.
Symptoms to Watch For
🐕 In Dogs
- Vomiting (often with blood), drooling, and severe diarrhea within 30 minutes to a few hours
- Wobbliness, tremors, and seizures
- Breathing difficulty and irregular heartbeat
- Collapse and death — even a lick or two of cream has been fatal
🐈 In Cats
- Vomiting, drooling, and diarrhea within hours
- Weakness, tremors, and seizures
- Breathing difficulty and irregular heartbeat
- Rapid collapse and death — extremely small amounts are lethal
What to Do If Ingested
- Go to an emergency veterinarian or call a poison hotline IMMEDIATELY — minutes matter.
- Prevent further licking; wipe any cream off the mouth and paws.
- Bring the cream tube or a photo of the label with the concentration.
- Do not induce vomiting unless a veterinarian instructs you to.
Steps apply to both cats and dogs. When in doubt, call a vet or poison hotline before acting. Have a cat? Run the Pet Poison Triage Wizard for cat-specific steps.
When to Call the Vet Immediately
Call your veterinarian or a poison control hotline right away if you notice any of these:
- ANY exposure — a single lick of the tube or treated skin is an emergency
- Vomiting, drooling, or wobbliness
- Seizures, collapse, or irregular heartbeat
Frequently Asked Questions
Frequently Asked Questions
How much 5-FU cream is dangerous?
Extremely small amounts. Fatalities have been reported in dogs from licking a few treated skin spots or chewing an open tube — a fraction of a milligram per kilogram in some cases. There is no antidote, and death can occur within 6 to 12 hours from seizures and cardiac arrest. This is the most lethal common topical medication in homes: treat any exposure as a race to the emergency vet.
My pet licked skin where I applied 5-FU hours ago and seems fine. Is that a risk?
Yes — even that counts as an exposure, and the cream remains on skin for hours. Do not wait for symptoms: call a veterinarian or poison hotline now. Symptoms can be delayed a few hours, and by the time vomiting and seizures appear, treatment options are limited. If your pet was treated with 5-FU at home, keep them away from the treated area until it is fully absorbed and washed.
How can I use 5-FU safely in a home with pets?
Apply it in a closed room away from pets, wear gloves, store the tube in a sealed container high up or in a locked drawer, and never leave the tube on a nightstand — chewed tubes are the most common exposure. Consider asking your doctor about pet-safer alternatives such as imiquimod or topical diclofenac if you live with curious pets, and dispose of used applicators where pets cannot reach them.
Sources
This entry is reviewed against the following authoritative veterinary sources.
Last reviewed: 2026-10-16