My 5mth old has a cold (i think). he had it for about a wk. but now he's sneezing, with a runny nose(which is sticky) & a cough. could it be allergies?

Prob not: Good question. I see allergies young, but rarely that young. Infants sneeze to clear their nose. Yours may be just mopping up the end of a cold, or even experiencing mild sinusitis. It's a myth that babies can't get sinusitis. Watch for prolonged wet cough and bad breath. But allergy, not likely. Keep an eye on your little one, though. ;)