A common cold is usually associated with a variety of symptoms in addition to a runny nose: cough, body aches, fatigue, and occasional yellow nasal discharge. All of these symptoms typically resolve in one to two weeks. Allergies occur immediately after contact with the allergens that provoke them. They're associated with clear discharge from the nose, nasal congestion, and itchy eyes, and the symptoms persist as long as contact with the allergens continues. Body aches are unlikely, but fatigue may occasionally occur with allergies. Your primary care physician can often help treat your allergies, but if specific testing is required to identify the cause for your allergies, or if symptoms are not adequately controlled with medicines prescribed by your doctor, then a consultation with an allergist is needed.