Hi, cough is an protective reflex. When any foreign particle tries to enter respiratory tract our body immediately responses to it in the form of cough. Try to take good air before going to bed. And keep your floor bed sheets always dry and clean(without dust particles). Avoid, for which you are allergic to. If it is due to infection you will have symptoms like throat pain or irritation ,fever,sputum colour change etc. In that case you have to take antibiotics. Consult general physician for furthur evaluation and treatment.