The Supreme Court in the case of Commissioner of Central Excise, Salem Versus M/s. Madhan Agro Industries (India) Private Ltd. has recently ruled that the coconut oil classified edible oil and 5% GST is applicable. 

However the question arises, whether coconut oil which is being used as hair oil is fit for human consumption? Who is the competent authority to decide the nature of edible oil?

If the hair oil pack contains the information that it is an edible oil that can be used for consumption/cooking and has Food Safety and Standards Authority of India (FSSAI) mark embedded on it then you will just have to pay 5% GST.  

Below is the pack of famous hair oil brand “Parachute”, the pack states that it is an edible oil  along with the FSSAI certificate.