By Claire Gillespie Updated Mar 24, 2022
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While Epsom salts are often paired with rubbing alcohol for home remedies, the chemistry behind the mixture determines how effective it really is. Understanding the differences in solubility between water and rubbing alcohol can help you make safer, more informed choices.
Epsom salts dissolve readily in water because of its high polarity, but they only partially dissolve in rubbing alcohol, which is less polar and has a bulkier molecular structure. This limits skin absorption and reduces the therapeutic effect.
Epsom salts are the common name for magnesium sulfate, a compound composed of magnesium and sulfate ions. Unlike true table salt, which contains sodium and chloride, magnesium sulfate plays a key role in muscle function, nerve signaling, protein synthesis, bone health, and DNA repair.
Water is a highly polar solvent, meaning it carries both positive and negative charge centers. This polarity allows it to attract the negatively charged sulfate ions and the positively charged magnesium ions, breaking the ionic bonds that hold magnesium sulfate together. As a result, Epsom salts dissolve quickly and completely in water, creating a clear solution.
Rubbing alcohol, typically isopropyl alcohol, is less polar than water and has a larger molecular size—often described as “bulky.” These properties make it less capable of surrounding and separating the magnesium and sulfate ions. When Epsom salts are added to rubbing alcohol, only a small fraction dissolves; most of the crystals remain suspended. Consequently, the concentration of active ions available for skin absorption is significantly reduced.
Beyond soothing sore muscles or treating sunburns in a warm bath, Epsom salts can be used orally as a laxative or to help extract splinters and bee stingers. However, ingestion requires careful dosing—too much can cause diarrhea, dehydration, or interact with certain medications. Always consult a healthcare professional before using Epsom salts internally.
