Why has my 4 month old been congested since birth?

Reflux?: Babies" nasal cavities are particularly narrow and are prone to be obstructed. The most common cause is just air dryness that causes the mucus to dry up and obstruct the nose. Next, is the common cold. Your baby could have been born with an abnormality. Last but not least, babies who have reflux often vomit through the nose as well.

Nasal congestion: At 4mo the primary cause of congestion are irritants or colds. House dust, fragrance, perfumes, detergent or cleaning products all leave scents that don't bother adults but irritate a babies nose. A good nasal clean out with saline can remove much of this irritant load, but removing the offending irritants from babies life helps more in the long run.Irritants aggravate colds ; nasal wash helps.