15 month old has had runny nose and watering eye for 3 days and now has a harshcough. is this his allergies?

Likely: It is likely that your toddler has allergies, probably to the spring pollens blowing your way! avoid using medications designed for older children- no antihistamines or cold meds. Use saline nose drops and a bulb syringe to clear his nose. A cool mist humidifier can help. Increase his clear fluids to break up the mucous. Call your doctor if fever >101 or not getting better in a few days.