Got fleas on your cat?
Ticks on your dog?
In deciding on a treatment - and yes, you do want to treat these little varmints - not all chemicals are equal.
Recently, the U.S. Environmental Protection Agency announced an agreement with two companies to take pet collars containing the chemical propoxur off the market.
After an assessment, the agency found "unacceptable risks to children" the first day after the collar is put onto the pet.
Here's the rub: The products won't actually be gone until 2016, if then.
Under the terms of the agreement, the companies, Sergeant's Pet Care Products Inc. and Wellmark International, can distribute the products until April 1, 2016. Even after that, stores can sell them until all are gone.
The EPA says the collars leave a residue on the pet's fur that can be absorbed through the skin of children who hug or pet the animal. Also, children can ingest the chemical if they pet the animal and then put their hands in their mouths.
The move came after the Natural Resources Defense Council sued the agency. It also asked for action on a second flea and tick chemical that the EPA did not address - tetrachlorvinphos, or TCVP.
"We've known for a long time that they're neurotoxic," said Miriam Rotkin-Ellman, a senior scientist with the national environmental nonprofit. "These products should not be on the market."
The chemicals, she said, cause an overexcitation of the nervous system. "That is what happens to the poor flea. . . . Its nervous system overfires."
Unfortunately, mammals have similar neuropathways, and the council says that the chemicals, in high enough doses, can interfere with the development of a child's nervous system - the smaller the child, the bigger the worry.
I found products with propoxur in a local big-box pet store, and the label bore a warning: "Do not allow children to play with collar."
The EPA specifies an additional warning: "Try to keep the pet away from your young children for a day after putting on the pet collar."
Caryn Stichler, a Sergeant's vice president of marketing, said the company was "pleased to be able to work with the EPA to resolve this matter amicably and ensure that our customers can continue to benefit from uninterrupted access to Sergeant's products."
Fortunately, much better products are available anyway, said Daniel Morris, a veterinary dermatologist at Penn's School of Veterinary Medicine.
In the last three or four years, there's been an explosion of products that attack parasites through enzyme systems that mammals don't possess. They have "amazing safety margins," Morris said.
Products are available through veterinarians and over-the-counter. They come in oral doses, on newer versions of collars, and as "spot-on" products applied to a small area of a pet's neck or back.
He suggested looking for products that contain imidacloprid and selemectin, which have been around a while, or those with newer compounds such as nitenpyram, spinosad, and afoxolaner.
Another game-changing development: The chemical fipronil, which until recently was the only tick protection available for cats, came off patent, so it's in a lot more products.
(Note: Don't assume it's OK to use a product for a dog on your cat. Permethrin, which kills ticks, won't harm your dog, but it's toxic to cats.)
Supposed "natural" remedies - such as brewer's yeast or garlic - are not effective, he said. Overall, it's important to limit your - and your pet's - exposure to fleas and ticks because they are vectors of disease.
Ticks carry Lyme disease, which can be a chronic, debilitating condition in some people. Fleas carry tapeworms and bacteria and can cause severe allergic skin reactions.
The flea, especially, is a formidable foe. One female lays up to 50 eggs a day, so if your pet has just 20 fleas, that could mean 1,000 eggs every day.
The eggs fall off your pet and hatch into larvae, which burrow into the carpet or hide under the baseboard. There, they wait.
When vibrations or an increase in temperature or carbon dioxide signals the presence of a four-legged hairy creature, Morris said, the insects emerge and seek the blood meal they need to survive.
That's why some people think flea products don't work. But, often, they simply didn't use a product for long enough. Or they didn't use one that has not only an adulticide, but also an "insect growth regulator" that will keep the eggs from hatching.
Morris advises pet owners to consult a veterinarian to determine the best flea and tick strategy.
"There's not a cookbook recipe . . . that works for every household," he said.
Some have only dogs. Or only cats. Some have both. Some have ferrets or rabbits as well. Lifestyle matters, too. If your dog swims every day, an oral product might be best.
The council says frequent combing, bathing and vacuuming can help. For more information on flea and tick chemicals, it has a product guide at www.greenpaws.org.
"GreenSpace," about the environment and health, appears every other week, alternating with Art Carey's "Well Being" column.