Each has a specific job to do. Think you could benefit? Read on to find out how to get one.

Ashley Jacobs, 31, was diagnosed last year with a rare blood condition that requires frequent doctor visits and blood tests—not good for someone who has a severe phobia of needles.

To manage her situation without full-blown panic attacks, the Newport Beach, California resident turned to an unlikely source: her 10-year-old golden retriever, Diamond. A mental health professional wrote a letter certifying Diamond as an “emotional support animal” so the dog could stay with Jacobs while she endured blood work and treatments.

“I feel much calmer when she's by my side,” Jacobs tells Health. “Diamond gives me something else to focus on aside from the fact that I'm about to get stabbed by a needle. Being able to focus on holding onto her leash as well as looking at her and petting her helps keep me from panicking. She's a mellow dog with a very calming presence.”

Emotional support animals (ESAs) have been in the news recently, with an increasing number of people relying on them for mental health issues. While cats, dogs, and other furry buddies are often designated as ESAs, some are way more exotic—think miniature horses, pot-bellied pigs, even a peacock. But why are they different than service animals? And how can you get one if you think they could help you? Here's what animal experts say.

What exactly is an emotional support animal?

Sure you may feel comforted when your dog curls up in your lap. But that doesn’t necessarily qualify your pooch to be an ESA.

“An ESA is a companion animal that a medical professional has determined provides a mental health benefit for an individual,” Ben Williamson, senior international media director at People for the Ethical Treatment of Animals (PETA), tells Health. “These might be people with anxiety, soldiers with post-traumatic stress disorder, or inmates with empathy issues.”

An ESA doesn’t necessarily have to be a Labrador retriever, a breed famous for its unconditional love. “Any living animal could be an emotional support animal. Support is just in the eyes of the beholder,” says Williamson. “Studies show a range of therapeutic benefits for people, from guinea pigs helping autistic children to llamas helping hospital patients.”

One in four people experience at least one mental health problem in their lifetime, Williamson points out. Those who do “often find it hard to talk to doctors or other humans. Sometimes all they really need is just a companion, someone they can love, take care of and look after, someone who will always be there for them,” he says. “Some people credit their emotional support animal as the only reason they're still alive.”

Still, because ESAs aren’t covered under the Americans with Disability Act (ADA), you can’t necessarily bring them everywhere—like when you pop into the supermarket, head to the gym, or meet up with friends at a restaurant for brunch. ESAs are allowed to live in housing that's been designated pet-free, though.

What’s a service animal, then?

Not a peacock, for starters. “There’s a lot of confusion around the difference between ESAs and service dogs,” acknowledges Nicole Ellis, a certified dog trainer and pet expert with Rover.com.

Basically, ESAs provide comfort and calming to their handler. Service animals perform a task. “A service animal is defined by the ADA as a dog that’s been individually trained to do work or perform tasks for an individual with a disability,” Ellis tells Health.

Miniature horses are also recognized by the ADA, but they’re not as commonly used. And some state and local laws define “service animal” more broadly to include other animals besides dogs.

The task(s) a service animal performs has to be directly related to a person's specific disability, whether it's physical, intellectual, sensory, or psychiatric. Guide dogs for the visually impaired are the most common example of service animals, but if you have diabetes, you may have a dog trained to alert you when your blood sugar gets too high or low. Some people with mental health issues have dogs that can remind them to take medicine, interrupt episodes of self-harming, or signal that a panic attack is about to hit.

Service dogs aren’t born knowing how to do all this. “Training can take a year or more,” says Ellis. “It involves basic commands, as well as public access commands such as ignoring people, food, and pets and being able to keep a calm focus in case of a medical alert.” Less than 5% of dogs are cut out for service dog work, she adds.

How to get an emotional support animal or service dog

While any animal can qualify to be an ESA, you need to get a legitimate written “prescription” from your healthcare professional to have one. Of course, like so many other things, you can also get your prescription from the Internet. Plenty of online sites sell the certification needed to designate a pet as an emotional support animal.

Getting a service dog or other animal is trickier. If you feel a service dog could help you, “the next step is discussing this with your doctor or treating therapist,” advises Ellis. “Your doctor is the only one who can determine if you meet the legal definition of disability, and whether you would benefit from having a service dog.”

If you're given the go-ahead, “the easiest route is to find a company—like Guide Dogs for the Blind, Canine Companions for Independence, Good Dog! Autism Companions, or Tackett Service Dogs—that already train service dogs and meet with them to review your needs,” says Ellis.

If you’re hoping to recruit your current pet into service, a good trainer can do an evaluation and let you know just how feasible that is.

And in case you were wondering, “it’s a felony to fake a dog as a service dog,” Ellis cautions. In fact, in some states, it’s punishable by a fine and jail time.