Only one pupil is dilated. Should I worry?

I'm not one to worry about most health issues, but I know this can be a huge warning sign.

So one eye is a little bloodshot which I'm 99% sure is allergy related. That started last night. I put in a couple allergy relief drops then, a couple more this morning. Nothing out of the ordinary. Then I put a couple in tonite, about 5, and around 630 I noticed that my pupil was dilated. I only put drops in the one eye and things have returned to normal now about 5 hours later. Never had any pain or numbness or any other symptoms. If I hadn't looked in the mirror, I wouldn't have known anything was out of the ordinary. I've used these drops before without incident but the web tells me that enlarged pupils can be a sideeffect. What do y'all think?