Consult a physician if nasal congestion lasts more than 10 ten days or if a high fever is present and lasts more than three days, suggests Mayo Clinic. Green mucus, especially combined with sinus pain or a fever, also requires a call to the doctor.
If you have emphysema or asthma or are taking medications that suppress the immune system, contact a doctor if you have sinus congestion, states Mayo Clinic. Call your doctor if you have bloody discharge from the nose or if a clear discharge appears after a head injury.
Congestion in babies can be serious, says Mayo Clinic. Consult a doctor if an infant under two months has congestion accompanied by a fever or if the infant is having trouble nursing or breathing because of congestion.