When it comes to providing entertainment and exercise for your dog—at no major physical or financial cost to you—few things can compete with a tennis ball. That said, it’s not a risk-free toy.

As Lifehacker explains, tennis balls aren’t made to withstand pressure from canine jaws determined to shred them to pieces, which could easily become choking hazards. Even if your dog does manage to swallow a small part or just the fuzz, that could end up causing a blockage in their digestive system. Tennis balls also may contain lead or other toxins that could be harmful to your pet.

The fuzz poses additional problems. Veterinary dental specialist Dr. Thomas Chamberlain told the American Kennel Club that the fuzz is a lot rougher than you might think, especially after it’s collected grains of sand and dirt—an unavoidable side effect of playing fetch. If your dog spends a lot of time gnawing on tennis balls, the fuzz can grind down their teeth and cause dental issues, which themselves can lead to worse problems. Exposed tooth pulp, for example, makes it easy for bacteria to enter a tooth and cause an infection.

All potential issues aside, there are still safe ways for your dog to enjoy the classic fetch vessel. In general, you shouldn’t let them play with tennis balls without supervision; and the Humane Society advises pet owners to promptly throw away any that start to show signs of deterioration. To guarantee that you can get tennis balls away from your dog quickly if need be, don’t use them for keep-away games.

And if your dog simply can’t resist tearing every tennis ball apart, you might want to surround them with safer toys, instead. Here are some guidelines from the Humane Society for choosing the best ones.

[h/t Lifehacker]