L.D.
My soon to be 3 year old too has allergies and asthma so I'm familiar with all this stuff. If his eyes have just been itchy the last few days, it's not the cat. my son was allergic to our cat and had bad eczema as a baby. It could be an allergy to pollen. I believe grass is bad now, at least where we live, in Minnesota. You could try giving him Benadryl and if it clears up then it's most likely an allergy. Although if it goes away on its own maybe something temporary in his environment that just bothered him for a short time. If you're really concerned, I would get him tested by an allergist. It helps a lot to know what their exact allergies are, then you can avoid his "triggers". Don't worry, all of this is very treatable and pretty common.