Minoxidil is only FDA approved for use on the head, so the application for beards is considered off-label use. However, a study into the effects of minoxidil on beard growth, published by The Journal of Dermatology, reported few adverse reactions resulting from using a 3% solution. There is also a lot of anecdotal support that it's safe for the face. While the risk is low, if you choose to use minoxidil for beard growth, it's best to be aware of the side effects such as irritation, itchiness, and dry skin.