G.B.
It does not necessarily mean he had pink eye. He could have had an eyelash in his eye that was irritating it. Or something else. I have very dry eyes and about once a month I get all red, swollen, and have goo running out of the corners of my eye. I do not have pink eye, I have a dry eye that got debris in it and it could not wash it out. When my eyes are like this I might take 4 showers a day and each time wash my hair and face very well. I can react to dust, dog or cat dander, perfume if I get close enough to it, make up flakes, sand, just plain old stuff in the air too like pollen or even poison ivy. It doesn't have to be pink eye just because he had a reaction, it could be a lot of other things too.
I suggest that next time you take him to the doc and get him looked at. The ointment for pink eye can really make the eye irritation feel so much better instantly. If it's a reaction or something in the eye itself the doc can see that and perhaps remove it sooner.