Suggest Medication For Cough,runny Nose And Bloodshot Eyes

My 21 month old son has been suffering from what I thought was yet another summer cold. But along with the lingering cough and runny nose, he now has developed bloodshot eyes. While putting allergy eye drops in his eyes, I noticed that each eyeball has an identical raised white bump, like a tiny pimple, in the center of the redness. A friend(nurse)recommended Benadryl, which I gave 2 doses of, andn the redness has disappeared, but the bumps are still there. No fever or symptoms other than the above mentioned "cold" symptoms. Any idea what this could be? We live in a very high allergen area in the midwest. Could this be a seasonal allergy?