Minoxidil is an FDA approved concentration for treating hair loss.  It comes in a liquid topical solution and is available over the counter for men. Minoxidil 5% is proven to grow 45% more than the Regular Strength 2% formula. It also begins growing hair back as quick as 2 months in many individuals.  The most common side effects are scalp itch and irritation, which are rare. The higher percentages of minoxidil are more difficult to compound and very rare to find. A stable non-greasy solution, which rapidly dries and absorbs into the scalp quickly and efficiently. The amount of success in hair regrowth is completely dose dependent. Which is why the 5% grows more hair back faster then the 2%, this is the same for the 10% & 15% strengths. Also while being in solution, this allows for greater absorption into the scalp then lotions, gels, or foams. The 15% is for those who can tolerate the 10% without any problems, or who have failed to regrow hair from the 2% or 5%. The extra 5% of minoxidil helps to recruit excess miniaturized hair follicles, and increases rate and thickness upon which the hair is regrown