But, you can't just apply rosemary oil on to the scalp. It would burn and also it is suggested that a carrier should be used with rosemary mainly because of that. I'm afraid that water also can't be used as Essential oils don't mix well with water. And for daily use I can't use other oils as a vehicle. Thus, I thought I may make DIY rosemary oil topical using alcoholIsn't rosemary a small enough molecular weight as an essential oil to pass through skin without a vehicle?