There are some studies on henna hair color and it’s ability to help regrow thinning hair on the scalp. There are no studies, to my knowledge, on the affects of henna on the brow area. However!...I have seen in two separate clients, obvious hair regrowth after regular henna tint sessions.
I believe in the results that I have seen, and encourage anyone that is bothered by thin or thinning eyebrows to give it a try. It’s an inexpensive service, compared to microblading, and could help to get you closer to your desired results.