If you only use conditioner, you could damage your hair and scalp. Conditioners are designed to be used after shampoo, as the shampoo helps to cleanse and remove dirt and build-up from the hair and scalp. Conditioner helps to seal in moisture and provide vital nutrients for healthy hair growth. If you only use conditioner, it won’t be able to remove the dirt and build-up from the scalp and it won’t be able to provide the proper nutrients for healthy hair growth. Therefore, it’s important to use both shampoo and conditioner for optimal results.