It can be necessary to take some Betaine (TMG) with the niacin for some people to prevent hypomethylation.
Hot shower and niacin.The hair shedding sounds like a histamine reaction. The histamine release lessens within a couple days.
Also just a general note - one should never take a hot shower during the time of taking niacin. This makes the histamine reaction almost unbearable.
Why?, because of to much heat?