Pear seeds, stems, and pits contain cyanogenic glycosides which can release cyanide and be toxic to cats.
Additionally, consuming too much pear can cause digestive upset.
Suggestions
If you decide to feed your cat pear, ensure that you remove all seeds, stems, and pits.
Offer only a small amount of the flesh as an occasional treat.
Note: even if labeled as safe, any food can potentially cause allergies. When introducing a new food, please feed a small amount and observe your cat for any allergic reactions.