Is a $175 Bella Lucca faux mink coat for dogs medically necessary?

Pricey couture is optional, but some breeds do need outerwear in the winter, veterinarians say. Small, short-haired, inactive dogs without a thick fur undercoat are more susceptible to cold weather.

Breeds include the Chihuahua, dachshund, Boston terrier, shih tzu, bichon frise, miniature pinscher and the xolo, a Mexican hairless dog.

'There's no question in winter with rain, snow and ice that these dogs are more at risk because of their size and inability to keep body heat,' says Rene Carlson, president-elect of the American Veterinary Medical Association.

Normal dog body temperature runs 101 to 102 degrees. A drop in body temperature of five or six degrees can put dogs at risk of low blood pressure and kidney damage, as well as decreased blood flow to the liver and brain, which can possibly lead to hypothermia.

Elderly or ailing animals may need to don extra layers, regardless of their breed, says Stephen Zawistowski, science adviser to the American Society for the Prevention of Cruelty to Animals.

There are plenty of pet apparel purveyors these days. Outdoor retailer REI sells $40 'Adventure Dog Boots' with recycled tire rubber soles, while etsy.com offers a crocheted acrylic/wool cap for toy breeds.

Bigger breeds bred for outdoor life and work, such as the Labrador retriever, German shepherd and Siberian husky, typically can stick it out in the buff, so long as they are active on walks or have a sheltered spot with lots of bedding and a nutritious, plentiful diet if left outdoors, vets say.

'When we think of the working and sporting dogs, these are the ones less likely to need protection,' Dr. Zawistowski says. 'Lap dogs need it the most.'

Useful garb may include: wool and polyester sweaters, fleece or waterproof jackets and booties to protect from ice and salted streets and sidewalks. Indoors, extra layers can help, too.

There are also bed warmers, such as the Pet-zzz-pad, an American Kennel Club-licensed item, with cords encased in steel chew-resistant casing.

Less useful, Dr. Carlson says: hats and goggles, which can throw off an animal's equilibrium. 'Dogs have a very good blinking response and a third eyelid that comes up if there's need for protection.'

Keeping Fido warm doesn't have to cost a fortune. A child's sweatshirt from a thrift shop cut to fit and bundled under a dog's belly with a zip tie can do the trick.

'When you're spending $250 on a designer coat, that's so you can be seen with the dog in the coat, not for the dog,' says Dr. Zawistowski says.