If used in the wrong way, collars can put your dog at risk of strangulation.

“A dog … can jump up and snag their collar on a fence post or a window latch,” which can lead to suffocation, says Dr John Pacy, owner of Healthy Pets House Calls, a mobile veterinary service in Palm Beach County, Florida. Hanging tags can also get caught on crates and other objects and cause choking, he says.

Even a well-fitting collar can be dangerous if used to tie up a dog in the backyard, says Dr Barbara Hodges, a veterinary advisor with the Humane Society Veterinary Medical Association. She says she has heard of dogs who tried to jump fences while tied on a long leash and ended up hanging themselves with their collar.

Apart from strangulation hazards, a collar can present other serious physical risks, especially if it’s too loose. For example, if a pet is “scratching its ear and the collar is loose, their back leg or their front leg could get stuck inside the collar, looped through,” Dr Barbara Hodges says. “It can lead to a limb breaking.” She has also seen dogs get their teeth or tongue stuck in a too-loose collar while grooming themselves, which can lead to broken teeth and other mouth injuries.

To avoid both physical injury and strangulation, a chest harness would be the perfect alternative.

A collar that is too tight can also be harmful to a dog, and even a “moderately tight” collar can lead to skin irritation, Hodges says. Collars that are too tight can cause hair loss, and the skin in those areas can be more prone to infection, she says.

In extreme cases, a very tight collar can cut into a dog’s neck. This can happen in cases of neglect when a puppy-sized collar is left on a growing dog, Pacy says.

In general, to protect your pup’s neck, it is always better to go for a chest harness instead of a collar.

Traditional collars can harm a dog’s neck if it pulls hard on the leash or if a pet owner uses the collar to pull the dog around.

“You are potentially damaging the dog’s neck by jerking it,” Hodges says. “The neck is a very, very sensitive area.”

Repeated stress on the neck can even lead to long-term medical issues—including damaging the thyroid glands and tissues around the neck area and salivary glands, she says. A chest harness is a safer alternative to neck collars that put a lot of strain on a dog’s neck, she adds.

Even if a collar does not lead to any serious injuries, the wrong collar can simply be irritating for a dog. Pet owners should use common sense when collar shopping. If a collar looks rigid and uncomfortable, it probably is, Hodges says.

“If you have a stiff collar on a dog, it would be like if we were wearing some piece of jewellery that was tight,” she says. “It’s going to impede their mobility and they’re not going to be a happy camper.”

Hodges says she has many clients who wonder why their dog is constantly scratching his head and neck. Of course, scratching can be due to several factors, but it can also be due to low-grade irritation from a collar, she says.