B.,
Mommy of an allergy toddler...and I am a hay fever mess too. But, here's the thing, you don't want to just medicate your child without knowing for sure. My son is on Singular daily and inhalers for the allergy related asthma that can rear it's head during pollen season.
Based on the input of my son's Pedi and my own ENT, I went with the simple solution of evaluating the symptoms and making sure it wasn't teething first. Molars can cause similar issues, and if he's teething he may just need time to get past that.
If you're really concerned it's allergies then, go with the allergy test to confirm it. I did a journal of instances and based on that the Pedi made his diagnosis. We were at the office ALL the time for runny nose and puffy eyes.
But, remember follow your instincts first!!