Why do I get a stuffy nose when I lie down?

The bedtime block is real and mechanical, and the proof is in the flip: lie on your left side and the left nostril blocks; roll over and within minutes the blockage switches sides. Mucus cannot do that - only blood flow can. MedlinePlus explains that a stuffy nose is swollen tissue lining the nose, the swelling caused by inflamed blood vessels. When you stand, gravity drains those vessels; lie flat and the pressure equalises, blood pools in the nasal lining, and the already-reactive vessels swell enough to close the passage. Whichever side is down collects more. If the lining is irritated to begin with - a cold, allergies, or the non-allergic rhinitis the NHS describes, where the inside of the nose becomes irritated and produces a blocked or runny nose in response to weather changes, perfume, smoke, alcohol, or spicy food - a small extra swell tips you from open to blocked. Practical relief stacks the physics back in your favour: raise the head of the bed or add a pillow so your head stays above your chest, rinse with saline before bed, keep the bedroom free of dust and fragrance triggers, and go easy on evening alcohol, which dilates nasal vessels. A pharmacist's decongestant spray works for a few nights, but MedlinePlus warns that using over-the-counter sprays for more than 3 days can make stuffiness worse - a rebound cycle worth avoiding. If one side is persistently blocked regardless of position, or the blockage comes with facial pain, nosebleeds, or has lasted weeks, a GP should look - polyps and a deviated septum announce themselves that way. Pymander is a free AI doctor, 24/7 by text, that can help you untangle yours.