How can you tell the difference between the common cold, allergies or sinus infection in a four year old?

Sometimes hard as... ...They can share some qualities, so it is important to see your doctor. Allergies are associated with sneezing, clear stringy nasal discharge and watery eyes; sinus infections may have fever, purulent nasal discharge and facial pain, with a cough usually worse at night and early morning, and symptoms lasting more than 1 week. A cold may have a fever as well and usually resolves in a week or less.