When introducing hair oils into your routine, the first thing you'll want to do is conduct a proper patch-test for any oil you are considering. Oils that show irritating effects during your patch-test should be entirely avoided on your scalp. For the oils that do work, you can begin using them by applying them as a scalp treatment and leaving them on for no longer than 30 minutes before effectively washing out. Do keep in mind when choosing oils that you want to pay particular attention to the comedogenic ratings and irritation scores. As a reminder, some scalps do prove to be sensitive to varying oils, even those that can help prevent hair loss. It's important to assess how your scalp fares with each oil you use.