Man’s best friend also happens to be man’s best co-worker - which is why more than half of millennial pet owners say they would consider changing jobs if it meant having an animal-friendly workplace.

The statistic, revealed by a survey by Wellness Natural Pet food, is just one of the reasons the annual event, Take Your Dog to Work Day, is celebrating its 20th year today.

The pet-friendly holiday occurs every year on the Friday after Father’s Day, and continues to grow as more companies become involved in the cause.

What is it and when is it?

The annual event, beloved by pet owners and pet lovers alike, is taking place today, Friday June 22.

As the name suggests, take your dog to work day is celebrated by bringing in canine office companions.

However, the day is about much more than spending time with fluffy employees - it was started in the hopes that people without pets would see the incredible bonds between co-workers and their pets and be encouraged to adopt a dog.

Who started it and when was the first?

Take your dog to work day (TYDTWD) was started by Pet Sitters International (PSI), a database for professional pet sitters and dog walkers, where dog owners can search free-of-charge for available pet sitters.

Dogs join their owners at work today (Karina Grimwade / SWNS.com)

The first event was held in 1999 and since then it has been a beloved holiday for both dogs and humans.

According to their website, PSI “feels that through the events, non-pet owners are able to witness the special bond their co-workers have with their pets firsthand and be encouraged to adopt a new best friend of their own.”

The first-ever TYDTWD saw an estimated 300 businesses participate.

Who participates?

Although PSI does not keep track of the businesses that participate in TYDTWD, as no registration is required, participation grows yearly - with social media posts acting as an indicator of the increasing popularity.

The pups are hard at work as they read emails and hold meetings (Allard Reisigner / SWNS.com)

Currently, there are more than 35,000 pictures tagged #takeyourdogtoworkday on Instagram.

However, only one in five people surveyed by Wellness Natural Pet Food said they work for a company that celebrates take your dog to work day.

Of the importance of having pets in the workplace, Chanda Leary-Coutu, director of consumer experience for Wellness Natural Pet Food said: “Not only are there proven benefits to having pets at work, like lowered blood pressure, lessened anxiety and increased physical activity, but it also helps attract and retain employees, especially among millennial workers.”

At the pet food company's own Tewksbury, Massachusetts office, the day is celebrated with dog grooming and massages, a biscuit bar, raffles, a jumpy house, K9 officer demos and more.

Today is the 20th annual Take Your Dog to Work Day (Mike Denman / SWNS.com)

Fortunately, the annual event has prompted a boost in year-round policies of animal-acceptance in workplaces, an office benefit that 37 per cent of Americans would sacrifice career benefits for, according to the pet food company's survey.

Amazon is one of these companies - with more than 6,000 dog employees showing up to the Seattle office for work each day alongside their owners.

Other pet-friendly companies include online commerce site Etsy, tech-giant Google, pet food manufacturer Purina, and Tradesy - where a Pup of the Month is selected each month.

In addition to increasing the chances of finding a forever home for the 6.5 million animals who enter animal shelters each year in the United States, Take Your Dog to Work Day benefits dogs, employees, and customers.

What should you know before bringing your dog to work?

If your company does participate in TYDTWD, there are some important tips to remember before bringing along your pup.

Confirming that the office space is safe for a dog is integral - which also means ensuring there are no exposed wires or other things to chew on.

It's also important to bring along snacks, water bowls, and other treats for your dog- as well as a bed if they have one.

Meeting a lot of new people can be tiring for dogs, so having a comfortable space for them to relax is necessary for a successful holiday.

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