But what happens when a seemingly "normal" handler brings a service dog around?
One woman, Jenn Bethune, received comments such as, "Yeah right, that’s not a real service dog”, and “Looks like anyone can put a vest on their dog and call it a service dog these days," in addition to the dirty looks thrown her way.
Some have also accused Bethune of wanting to bring her pet everywhere, under the guise of a service dog.
And Bethune acknowledges that it looks like everything is going swimmingly for her.
"Don’t I look fine? I look like I’ve got it all going for me. My hair is perfectly curled, my makeup is flawless, and I’m cute as a button in my favourite Disney attire. You wouldn’t think anything could even be wrong with me."
Fatal car accident
But not all disabilities are visible, she continues.
Eight years ago, Bethune saw her first-born son, six-year-old Ethan, die right before her eyes in a car accident.
The family — Bethune, her husband Kyle, and two sons — were on their way to a weekend trip for Ethan's birthday.
Some 15 minutes into the trip, they were hit by a truck. Ethan died immediately.
Kyle sustained bleeding in the brain, ruptured spleen, and three broken ribs.
Bethune and her younger child walked away with minimal physical injuries.
But since then, the scene of Ethan dying has been repeating in her head every single day — a symptom of PTSD (post-traumatic stress disorder).
As a result, Bethune experiences night terrors, severe anxiety, as well as random and unpredictable panic attacks.
Countless hours of training
Bethune's service dog, named Theodore, senses when she's having a panic attack.
He then calms her down by leaning in and putting his nose to hers.
According to Bethune, this brings her back to reality without the use of "seriously addictive medication".
When Theodore is "working", he does not bark or get distracted by his environment and other dogs.
Instead, he gives his full attention to Bethune.
However, in order to be so attuned to Bethune's needs, Theodore had to go through "countless" hours of training at the dog academy.
But the service dog has given Bethune a new lease of life.
"Having Theodore has given me my life back. I don’t have to live in fear of my panic attacks any more. I can travel anywhere I want and when I do have a flashback to the accident, Theodore leaps into action and knows exactly what to do."
Bethune wrote the post in hopes of opening minds to invisible disabilities, and to help others who have experienced people who were similarly rude to them and their service dog.
"Just remember, you never know what disability someone has by looking at them on the outside, so don’t be an as*hole."
You can read the Facebook post below and her blog post here.
Top image via Red White & Bethune/Facebook