Flesh of oranges is non-toxic in small amounts, but peels, seeds and oils are irritating. Lemons and limes: avoid.
Cats are sensitive to the essential oils (limonene, linalool) and psoralens in citrus — all parts should be avoided.
Citric acid and essential oils irritate; cats are especially sensitive.
ASPCA Animal Poison Control: (888) 426-4435 · Pet Poison Helpline: (855) 764-7661 — 24/7, a fee may apply. Your own vet first when reachable.