Fennel

Fennel (Foeniculum vulgare) is non-toxic to cats. It is classified as generally safe, meaning it does not contain compounds known to poison cats.

Most cats will have no reaction at all. If your cat eats a large amount of fennel, the fibrous plant material may cause mild gastrointestinal upset such as vomiting or diarrhea.

There is no established toxic dose because fennel is non-toxic, but large quantities of any fibrous herb can irritate a cat's digestive tract. If your cat ate a significant amount and shows persistent vomiting or diarrhea, contact your veterinarian.

Fennel has a strong anise-like scent that some cats find interesting or appealing. Occasional sniffing or nibbling is not a concern, but non-toxic does not mean eating large amounts is harmless — GI upset is still possible with excess consumption.

Fennel (Foeniculum vulgare) is non-toxic to dogs. It is generally considered safe, so a dog that nibbles on the feathery foliage or fronds is not at risk of poisoning.

Fennel itself is not harmful, but eating a large quantity of any fibrous plant material can cause mild gastrointestinal upset — vomiting or diarrhea — as your dog's digestive system handles the bulk. Small amounts are unlikely to cause any reaction.

Monitor your dog for signs of digestive upset such as vomiting, diarrhea, or lethargy. Because fennel is non-toxic, a small amount requires no action; if your dog ate a large quantity and symptoms persist or worsen, contact your veterinarian.

The classification data does not distinguish between plant parts, and fennel is considered non-toxic overall. That said, concentrated forms like essential oil are far more potent than the whole plant and are best kept away from pets entirely; stick to the whole herb in small amounts.