In the US and UK the market for clothing for pets is growing. But is it a sensible bit of indulgence or an inappropriate fad, asks Helen Soteriou.
Anyone going into a park during the recent cold weather might very well have seen dogs wearing winter coats.
Clothing for pets is a booming market with spending expected to break the £30m mark in 2012 in the UK, according to market research firm MTW Research.
In the US, the trend is even more pronounced. While in the UK a retailer like Argos might sell only functional winter jackets for dogs, at a US retailer like Target you can buy everything from a colourful polo shirt to stegosaurus-themed fancy dress costumes.
There is a long tradition of very specific functional clothing for animals. Ancient Greek armies would put leather boots on the feet of their horses to protect them against snow. Police animals can be dressed in fluorescent covers.
But now less functional clothing is becoming a boom industry, with boutiques offering all manner of exotic outfits.
Louis is a dog. He is also the face of two pet boutiques in west London's Notting Hill, run by his owner Andre Carless.
A fashion designer by trade, Carless initially used fabric off-cuts to make T-shirts for dogs. When he moved into co-ordinated ranges for men and dogs, the dog range took off and encouraged him to specialise.
"Louis is the inspiration for everything I do," Carless states. "I kept making things for him and people kept asking me 'where did you buy that?' and I knew people were interested in that."
The pet clothing market is broadly divided between "practical" and "indulgent" items.
The RSPCA's position is that clothing is appropriate for animals in some circumstances. For old, bald, thin, tiny or ill dogs a layer to provide warmth or waterproofing in cold weather may be beneficial.
Greyhound and whippet owners have long used coats for them in very cold weather in much the same way a horse owner might use a blanket.
"There can be clear benefits from animals wearing some forms of clothing such as for warmth and waterproofing," says the RSPCA. "However, functionality must always come before fashion and the clothing must have a clear welfare benefit when dressing animals."
The market ranges from highly indulgent products to what is termed "functional pampering", says David Lummis, senior pet market analyst at research firm Packaged Facts.
"The more interesting products of recent years are those geared toward senior and other special needs pets, meeting real needs such as protecting the paws, and keeping the pet warm while treating joint conditions."
You can find "therapy jackets" for pets with aches and pains including hip dysplasia and canine arthritis, he says.
In 2012, MTW Research estimates that sales of pet clothing will top £30m for the first time, hitting £35m by 2015.
But spending on pet clothes is not all functional and it's not all aimed at dogs. Carless stocks products ranging from sun visors which can be worn by cats that have sight problems to cashmere jumpers ideal for hairless cats who feel the cold.
Some people are buying items only to momentarily dress up their animals for a photo shoot.
US firm Kitty Wigs offer wigs for cats. They come in three different colours - Pink Passion, Silver Fox, and Electric Blue.
Owner Julie Jackson and her muse, a lilac-point Siamese named Boone, offer purely indulgent items, which she says are strictly photo props. Her website advises "if your cat's not initially interested, don't force it" and suggests starting with a can of food to encourage co-operation from the cat.
But do cats and dogs really love the attention or does the clothing craze say more about the owners' needs?
The RSPCA warns owners that animals are not accessories and says that clothing should not restrict movement or affect their ability to relieve themselves.
But there's a more complicated problem.
"The animal would be aware that something is being done to it, the same as when a collar is being put on. If the animal appears to tolerate the attention and fuss of being dressed up, then as long as it can perform normal functions ie walk, toilet, rest then there is not a welfare issue," says clinical animal behaviourist Pippa Hutchison.
"I have a problem, though, when it comes to communicating with other dogs - it is hard enough for dogs to 'read' the body language between different breed types. Therefore, potentially there is a problem here. A 'dressed up' dog may not be understood and another dog may be aggressive towards it, or the 'dressed' dog may get frustrated in the presence of other dogs and become aggressive itself."
The reasons why pet owners dress up their pets are not yet well researched.
"There would be a long way to go before these fads could be said to be anything more than just fads," says Dr Helen Barrett, developmental psychologist and research fellow at Birkbeck College, University of London. "The anthropomorphising tendencies that some, if not most people at some point, have in relation to their pets doesn't necessarily indicate a fundamental shift in the way those people value close human relationships."
Those who choose not to dress up their pets probably have their own explanations for the trend.