
First off find out what it is sets you off.. saliva.. hair... dander? I know people who cannot let a dog lick them but are fine stroking them.
Then narrow down your coat types, then spend LOTS of time in houses with dogs of those coat types, and ask the owners NOT to hoover up etc before you go so you really will know if you are allergic (ie if they have a fairly hairy house and you dont react... you are unlikely to!).
I recently helped my friend get a dog, she previously had assumed she was allergic to ALL dogs, as she has fairly severe (read 'liable to be hospitalised') reaction to her friends greyhounds, and also to labradors and previously to family collie x.
She has very severe asthma and excema.. we found her a dawg though.. a wire haired lurchery type dawg.
Prior to meeting him, she spent a week in my house which is UBER hairy, with a smooth short coated dog, a medium coated collie, a wirey haired terriery dog and a linty haired lurchery dog... and she had barely ANY reaction at all to that lot (and when i say uber hairy.. i do mean 'i clean when i cant see the colour of the floor any more, im allergic to cleaning).
So that told us she was absolutely NOT allergic to 'any' dog, but to specific coat types and if she was in very close contact with my smooth haired dog that did set her off.. with the wirey ones she could have them on her lap!
The other thing to consider is, do you have a lot of soft furnishings, ie carpet, sofas etc... I do not and friend and I do think this is a major part of why she had barely any reaction in my house - soft furnishings hang on to allergens. Hard floors, throws on sofas you can properly wash etc is the way to go.
It is also i think more likely that you will become used to your own dog, so you may have a mild reaction that becomes less and less - it wont make you then not react to other dogs, but you should become 'immune' to your own (doesnt always work but very often does).
Im allergic to cats.... but not my own!