Sinusitis, which is the swelling of the sinuses, is common after you have had a cold or the flui. Once the sinuses start to swell it can stop mucus from draining properly, giving you a feeling of sinus congestion.
According to the NHS, you may experience other sinus infection symptoms such as green or yellow mucus coming from your nose, a reduced sense of smell or a high temperature.i There might also be other, less obvious symptoms, like bad breath or toothache (or, in young children, irritability or difficulty feeding).i
You may also find that signs of sinus congestion come with some sinus pain, which can occur as a result of the inflamed sinus opening.ii This may be due to an infection, allergy, irritant or structural abnormality.ii