My 1yr old has an itchy fine rash on his face and lower back. its fine pimples, reddish in colour. any recommendations on something i can get otc?

Just monitor it: This could easily be a reaction to something he ate/drank or as yet unknown exposure. Most will fade over time (food rxn 3-4 days) and others a variable interval. The generally fade in spite of anything you so it is okay just to ignore it for now & see what happens. A bit of diphenhydramine may help with any itching. (1 tsp/25 lb)