Why does post-nasal drip cause a bad taste?

Post-nasal drip means mucus from your nose and sinuses sliding down the back of your throat around the clock - MedlinePlus notes excess mucus running down the throat causes cough and sore throat, and the NHS calls the build-up catarrh, usually triggered by an infection, allergy, or irritation. The bad taste is chemistry done by bacteria. Your mouth and throat host hundreds of bacterial species, and a steady supply of protein-rich mucus is a buffet: as they break the mucus down, they release compounds that taste stale, salty, sour, or faintly rotten - strongest in the morning after hours of undisturbed dripping, and worse if you mouth-breathe and dry everything out. Sinus infections sharpen it, because infected mucus carries its own flavour and odour. The taste is a symptom of the drip, so treating the drip treats the taste: saline rinses or a saline spray flush the mucus out before it descends, hydration thins it so it clears instead of clinging, steam loosens it, and propping your head at night reduces the pooling. Tongue-brushing helps the morning version directly, since the back third of the tongue hosts most of the bacteria. If the drip follows hay fever, an antihistamine or steroid nasal spray from a pharmacist addresses the source. The NHS advises seeing a GP if catarrh lasts longer than a few weeks - chronic post-nasal drip deserves a look for sinusitis, polyps, or allergy. Blood in the mucus, one-sided facial pain, or a high fever alongside are also review triggers. Pymander is a free AI doctor, 24/7 by text, that can help you find the source.