According to doTerra - it's one of the most potent herbs for boosting the immune system but it's also wonderful for relaxation and mood enhancement.
An herbal expert once explained to me that it, "helps the body remember how to be whole" and recommended a few drops of Frankincense under the tongue when feeling like something is coming on or when healing from a chronic sickness.
A doTerra blog lists "Fifteen uses for Frankincense" which I rather liked.
DoTerra is a great brand to buy - but their Frankincense oil is quite expensive ($80+). My mentor mentioned to me another brand whose frequency is the same as the doTerra brand but whose price is much more affordable. (This info. applies to the Frankincense oil in particular - I'm not sure about it being so for other oils.)
For me, this is an oil I like to make sure I have in our home and have extra of for our food/emergency storage.
Disclaimer: Although I love the doTerra oils - I do not sell them.