There are many ways to remove tear stains from cats, including the following:

1. Regularly clean the eyes: Pet owners can regularly wipe their cat's eyes and surrounding skin with a towel or wet wipes. This effectively reduces the time eye secretions stay on the skin around the eyes, thus greatly reducing the chance of tear stains.
2. Unblocking the nasolacrimal duct: If the cat's tear stains are severe, it is mostly due to a blocked nasolacrimal duct. In this case, we can take the cat to a professional veterinary hospital to unblock the nasolacrimal duct.
3. Use boric acid powder: For deeper tear stains, we can usually mix boric acid powder with water and apply it to the tear stains, which is very beneficial for them.