Fever or aches
Both colds and allergies
can give you a runny/stuffy nose and coughing, but if there are aches or a fever
it's a cold (though not all colds will cause fever and aches).
Colds tend to last less than 7 to 10 days, allergies can last weeks to months - or if it's an acute exposure to something your allergic to, it may only last minutes.