Ancient Minerals Magnesium Flakes are ideal for use transdermally (i.e., acting across the skin surface) enabling the body to absorb as much magnesium as it may require. Unlike oral magnesium supplementation (which is characterized by certain limits on the rate and amount of uptake and assimilation), magnesium applied directly on skin via baths or footbaths (i.e., transdermal application) can rapidly and effectively raise tissue (and cellular) levels of magnesium.