1. Reasons why babies sweat while sleeping. Babies sweat while sleeping because the body\’s metabolism slows down and the body temperature drops during sleep. Sweating is a way for the body to regulate body temperature. In addition, babies\’ skin is thin and rich in blood vessels, which makes them sensitive to temperature changes and prone to sweating. It may also be caused by too much heat. 2. How to prevent your baby from sweating while sleeping 1. Wear clothes with good breathability: In summer, you can choose cotton or linen clothes, and in winter, you can choose pure cotton or wool and other materials with good warmth and good breathability.