Magnesium absorption, as well as magnesium deficiency in our diets, is problematic. The soil in most countries has been farmed to a point of magnesium depletion. Furthermore, magnesium salts are laxatives, so they can lead to a more rapid gut transit time, not allowing gut absorption.
When taken orally, magnesium may be absorbed inefficiently due to the a) laxative effect of oral doses; b) effect of other foods, vitamins, or minerals in the gut that lessen absorption; and c) individual differences.
Transdermal therapy, via footbaths or spray, creates “tissue saturation”, which allows magnesium to travel to the body’s tissues and cells at a high dose without losses through the gastrointestinal tract.