For males, Minoxidil works best in the vertex and mid-anterior areas. Some males can regrow hair in the hair line but most males cannot. If you do not have thinning in the vertex and mid-anterior areas, Minoxidil is not appropriate for you. If you are female, Minoxidil can work anywhere on your scalp, including the hair line.
Every medicine has possible side effects and Minoxidil is medicine. It does not matter where on your head you use it as far as the possible side effects are concerned.
To help you reduce the possibility of experiencing the possible side effects - and to reduce the emotional impact of shedding, taper up to the twice a day dose slowly over time. Start with once a day every other day for a while. The once a day every day for a while. Then alternate between once a day and twice a day for a while. Then finally use it twice a day as directed.
If you decide to stop using Minoxidil, taper off of it the same way in reverse to prevent inducing a dramatic shed that can happen if you stop abruptly.