Hair serums and oils are usually recommended for people with dry or frizzy hair. The main benefit of using these products is that they can help to moisturize and condition the hair, making it softer and smoother. Additionally, hair serums and oils can help to protect the hair from damage caused by heat styling or environmental factors. In general, these products are used on wet or damp hair, before blow-drying or styling. They can also be used on dry hair to provide a bit of extra shine and protection. When selecting a hair serum or oil, it is important to choose one that is suitable for your hair type.