It is because of increased mucus production in the lying down position by the airways.
When you lie down, mucus from the nose and sinuses, can drip down the back of the throat, triggering a cough reflex. This is common in conditions like allergies, colds or sinus infections.
Health Tips
•Elevate your head, use extra pillows or a wedge to keep your head elevated can help reduce postnasal drip and acid reflux.
•Hydrate and humidify drinking water, and using the humidifier, can keep your throat, moist and reduce irritation.
•Allergen control Keep your sleeping area clean and free from dust dander and other allergens•