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.