Is it better to have your hair underneath you or on top when sleeping?
Generally, it is better to place hair above the body rather than underneath while sleeping, as this helps reduce scalp discomfort and hair damage. However, the ideal position may vary depending on hair length and personal habits. If you have concerns, it is advisable to consult a healthcare professional in advance. Detailed analysis is as follows:

For individuals with long hair, keeping hair above the body is more suitable. When long hair is pressed under the body during sleep, it can easily become tangled or experience friction due to turning over, leading to cuticle damage, dryness, and knotting. Over time, this may also pull on the scalp, causing mild pain or affecting local blood circulation. Placing hair above the body allows it to lie naturally and freely, reducing these issues.
People with short hair or those accustomed to sleeping with their hair compressed can continue their current practice if they experience no discomfort. Short hair is less prone to significant friction or pulling when pressed under the body, and typically does not lead to noticeable damage. As long as there is no scalp soreness or frizzy hair upon waking, there's no need to deliberately change the habit—sleep comfort should be the top priority.
When choosing how to position your hair, consider using soft, breathable pillowcases to minimize friction between hair and fabric. Gently combing hair before bed can help prevent tangling. If you frequently experience scalp discomfort after waking, try adjusting the position of your hair during sleep and observe whether symptoms improve.