Lemons are harmful to cats. Cats have a keen sense of smell. Lemon has a strong pungent smell. Cats may feel uncomfortable after smelling it. They generally don't like the smell of lemon. Citric acid is highly acidic. If a cat accidentally eats it, it will irritate the gastrointestinal tract and may cause vomiting, diarrhea, depression, or even death.

Fruits that cats cannot eat:

1. Grapes. Grape contains high sugar content, which can damage the cat’s kidneys and cause diarrhea, vomiting, etc.

2. Lemon, grapefruit, orange, etc. Oranges, grapefruits, lemons and other types of fruits contain ingredients that are irritating to cats and can cause gastrointestinal discomfort in cats.

3. Peach, apricot, plum, etc. This type of fruit can cause digestive tract diseases in cats, causing diarrhea and vomiting.

4. Mango. Mango belongs to the Anacardiaceae family and contains many substances that can cause allergies in animals, which can cause itching, inflammation or difficulty breathing in cats.

5. Figs. The fig glycoside contained in figs can also cause allergies in cats.

6. Papaya. The "papain" in papaya can cause allergies in cats and can easily cause oral inflammation or breathing difficulties.