I wish to know if hashish oil is allowed to apply on hair as a nourisher. May Allaah reward you for your guidance. Ameen

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

We do not know the reality of this oil you inquired about, its ingredients and where it is extracted from. However, there is a Fatwa in "Islamtoday website" about its use.

The Fatwa reads: “All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger as well as that of his family and all his companions.

The word hashish refers to cannabis which has a flower or fruit at its top, from this flower or fruit, the narcotic resin is extracted by distillation, pricking or piercing. Hashish is in principle a pure plant and it does not become narcotic except after treatment, its oil is also pure in principle as it is extracted from a pure plant. This oil is not narcotic and does not cause any drunkenness nor is it a downer, so it is permissible to possess it and apply its oil to one's hair provided no intoxicant is added to it. However, when it is confirmed that consuming this oil causes intoxication, then it is not permissible to get possession of it even for the purpose of oiling the hair with it, as this is a means that tempts a person to be intoxicated by it.”

Allaah Knows best.