Yes you can be allergic to one breed of dog and not be allergic to another breed of dog.
Some dogs are also hypoallergenic which means that the hypoallergenic dogs produce less dander and cause fewer symptoms in people allergic to dogs.
So if you're allergic around a dog then they're usually not hypoallergenic and if you can be around another breed of dog without getting allergic then that dog is most likely a hypoallergenic dog.