Consumers using over-the-counter flea products should be careful to read the product's label, cautioned David Housewright, business manager for Ashland, Ohio-based KenVet Professional Veterinary Co.

"Be sure to read the caution statement, the ages of animals it can be used for and the list of ingredients," said Housewright. "And as with any insecticide, it's not a good idea to use flea products around fish, ponds or birds." Many manufacturers now offer toll-free numbers for consumers with questions about their products, or about flea control in general.

Cat owners should avoid products not labeled as safe for use on cats, Dr. Sinclair added. "Dips made for dogs, for example, can have organophosphates in them that can be very harmful to cats," he said.

Go gently, especially when using spray products, recommended Jeanne Berg, supervisor for The Ark Pets and Supplies pet store in Washington. "In America, some people feel more is better," Berg said. "We had one lady who just drenched her kittens with flea spray, and then she wondered why they weren't feeling so good!"

"A lot of people overuse ectoparasiticides," agreed Tanya Grey, marketing manager for DVM Pharmaceuticals. "They'll put a collar on their pet and dip it and treat the environment without being careful to choose products that are designed to work together."

Although products containing pyrethrins or pyrethroids are generally considered safe, on rare occasions some cats may be sensitive to these products, said Hilty Burr, DVM, managing veterinarian with Pfizer Animal Health's companion animal division. Sensitive cats may show symptoms of toxicity including depression, excessive salivation, muscle tremors, vomiting, incoordination, labored breathing and loss of appetite, Dr. Burr said.

"Unfortunately, there are some cats in very rare cases that are sensitive to even small amounts of these products," Dr. Burr said. "The good news is, if your cat does have signs of a sensitivity reaction, washing the product off with soapy water is usually all that's needed for the problem to resolve. If that is not enough, seek prompt supportive treatment by your veterinarian."

Instead of spraying a flea product directly on the cat, Berg recommends spraying a towel and then gently wrapping the cat's body, leaving the cat's head uncovered.