Using hot water on the head may aggravate a cough, cold and even your sinuses | Yoga of Eating
Avoid wetting the top of your head with hot or very warm water. It can be bad for your sinuses and may cause cold and cough. Use mild, lukewarm water or room temperature water instead. Regular usage of very warm, hot water on the crown may manifest in the body as excess mucus, cough, asthma, sluggishness, laziness and perhaps even delirium.