Allergic to dogs???

I'm not allergic to anything. So I thought. But over the past 2 nights I have been to 2 friends houses and gotten very congested. These friends share 2 things in common with regards to their living arrangements.
Both live in Cedar Park. Both have a dog.

I've never been allergic to cedar, and though Barbie has 2 huge cedars in her back yard, I don't recall Mike and Tara having any in close proximity to their house. And both times I was indoors the whole time. I've spent time at Barbie's house before she had the dog and didn't notice the congestion.

So that leaves the dogs.

Could I have suddenly developed dog allergies?
Could it be pregnancy related?
If so, will it go away afterwards?

As soon as I got home, the congestion went away. Maybe sweet kitties are the antidote?