When using frankincense oil on your skin you should dilute the frankincense oil with some carrier oil before applying it to skin.
If you apply frankincense oil directly to your skin without diluting it then you can get skin irritation or burns from the frankincense oil.
Always dilute any essential oils before applying the essential oils to your skin because they can burn your skin and causes rashes and irritation.
You can use olive or any other type of carrier oil to dilute the frankincense or other essential oils in first and then apply it to your skin.