Yes, you can apply hair oil the morning after using Dermadew Hair Serum the previous night, especially if you're planning to wash your hair that day. Dermadew Hair Serum is typically lightweight and designed for overnight use to nourish the scalp and hair. Applying hair oil the next morning can provide additional moisture and nourishment. However, it's important to use hair oil sparingly, as excessive application can lead to buildup and may require more frequent washing. If you have concerns about product buildup or scalp sensitivity, consider alternating between using the serum and hair oil on different days to maintain a balanced hair care routine.