It can feel like a cold drags on when symptoms such as a cough or congestion outlast the main illness, which is normal as the airways heal over two to three weeks. Catching a new virus soon after the first one, common in winter or around young children, can also make it seem like one endless cold.
Sometimes persistence signals a complication. A bacterial sinus infection may cause facial pain and congestion lasting beyond about 10 days, and a chest infection can cause a worsening cough with fever and breathlessness. Allergies or other conditions like asthma can mimic a cold that never fully clears.
If symptoms persist beyond about 3 weeks, keep worsening, or come with high fever, facial pain, breathlessness, or coughing up blood, see a doctor for assessment.