When it comes to allergies, it's a complete crapshoot - there is no "universal rule", or even "general rule with some exceptions". It's damn near totally idiopathic - This guy over here who knows he's allergic gets itchy when he pets a dog. This gal over there breaks out in hives and starts swelling up like the kid that turned into a giant blueberry in Willy Wonka if a dog licks her hand, yet before that incident, she'd been surrounded by and interacting with dogs all her life without even a hint at a problem. This other guy on the other side of the room gets watery eyes and a mild choking sensation if a dog walks into the room, and has for years. Yet another gal drops dead of anaphylactic shock 15 minutes after she stumbles across an abandoned puppy and picks it up to take it inside out of the rain - but she's never had any indication she might be allergic. This other guy has been letting dogs fuck him for years as a matter of routine - suddenly, with his dog stuck up his ass the same way he's been dozens, perhaps hundreds of times before, he starts wheezing, his throat starts closing up, and 5 minutes later, he's stone dead, with the dog standing there wondering what the hell is going on, still stuck up his ass. This gal over here starts having breathing difficulties if she walks by a dog-grooming shop that has the door open, but is otherwise never bothered by being around dogs, and in fact, like having her standard poodle put the bone to her on a regular basis, and never seems to have any problems - Apparently it's only doggy-dandruff she's allergic to, and since poodles are known for being low-dander dogs, she gets away with it. But let a shep or a pitty climb up on her back, and she starts trying to choke to death on her own snot.
Similarly, MAYBE - in great big flaming letters forty feet tall - there are drugs/treatments that help *THIS* guy, but they don't do a damned thing for *THAT OTHER* guy - or even make things worse for him. What's the difference? Take your best guess! It's as likely to be right as anybody's.
In short, if you know you have allergies to <insert critter of your choice here>, *OF ANY SEVERITY WHATSOEVER*, you're basically playing russian roulette if you try having sex with one. How many chambers are loaded in this particular gun? Who knows? Might be none, might be the standard 1, might be all 6. You spin the wheel and collect your prize. Maybe that prize is a nice fuck, with nothing worse than a little itching or burning for a couple hours after, if that much, maybe it's a spiffy new apartment in the local boneyard - one about 6 feet long by 4 feet wide by 6 feet deep, and absolutely no view of anything but dirt and worms (maybe some rocks, depending on the local soil composition) in every direction.
There's simply no way to say anything more certain on the topic, specifically because allergies are so totally individual.