Neem oil, while generally considered safe for dogs, may be harmful to cats. If ingested, it can cause vomiting, diarrhea, lethargy, and tremors. Cats are sensitive to certain compounds in neem oil, including salannin and nimbin. These compounds can cause irritation or harm to the cat’s digestive and nervous systems. If you suspect your cat has ingested neem oil, contact your veterinarian immediately.