Hypoallergenic dogs are real somewhat but there are no 100 percent hypoallergenic dogs because all dogs do shed their fur and create at least some dander.
The dogs that are considered to be hypoallergenic though tend to shed less fur so they produce less dander which makes them great dogs for people who suffer from dog allergies.
But you can still be allergic to dogs that are considered hypoallergenic but you're less likely to suffer dog allergies when around a dog that sheds less fur and is considered to be hypoallergenic.
But that's really all a dog is when it's considered hypoallergenic is that it's fur is shorter usually and it doesn't shed as much as it's fur as other dogs do.
The only true dog that would be hypoallergenic would be one that likely has no fur at all.
But then again even skin particles can come off the dog when they shed a bit of skin or scratch their skin and send the skin flakes through the air.
Then you could be allergic to that skin.
If you're allergic to dogs and still want a dog then getting a hypoallergenic dog may be the way to go and you usually won't suffer allergic reactions to those dogs but you sometimes can.