Abstract: The present invention provides a composition of matter which has been demonstrated to be a very effective treatment for acne, seborrheic dermatitis and related skin diseases when applied to and contacted with affected skin areas, while avoiding the disadvantages and complications attendant to more established treatments. The composition comprises a synthetic mixture of salts which, when dissolved in a solvent such as water, is ionically composed primarily of a mixture of sodium and magnesium cations and chloride and sulfate anions, and which is preferably free of added zinc. More specifically, the salt mixture according to the present invention comprises the following range of composition in grams/kilogram of salt mixture in the ionic state, the balance being water of hydration: I.