Hello Mr. D Piers
is usually due to allergy
which can be due to changing weather, pollen, dust or any other allergens. To get rid from the problem follow some precautions so that it cannot reoccur:
1. Protect yourself form changing cold weather.
2. Keep yourself warm in cold climate.
3. Change your home linens every week.
4. Wear mask when you go outside to protect yourself from dust, pollen etc.
5. Take steam inhalation and try to expel out as much phlegm as you can.
6. Consult your ENT specialist
so that he/she may check you for any anatomical reasons.
Hope this will help you.