top of page


Are magnesium hydroxide (Mg(OH)2) and magnesium oxide (MgO) the same?

- They are not the same, although they are very similar in function and structure.  Magnesium hydroxide, Mg(OH)2, has a more predictable reaction when used as an industrial neutralizer.  Magnesium hydroxide is the aqueous suspension of magnesium oxide and can be chemically transferred back and forth by heating and rehydrating.  In certain applications, magnesium oxide, or MgO, is more reactive due to the absence of H2O.  

Is magnesium hydroxide, Mg(OH)2,  hazardous?

- Magnesium hydroxide is non-hazardous and is considered a safer alternative to other dangerous industrial neutralizers such as sodium hydroxide (caustic soda) and calcium hydroxide (hydrated lime).  Pharmaceutical applications, including antacids and laxatives, as well as food additives and dietary supplements, require a purer grade Mg(OH)2 to comply with USP and FCC standards. High purity Mg(OH)2 is safe for human consumption and absorption as per product guidelines, and always under the supervision of one’s health care provider.

Does magnesium hydroxide powder dissolve in water?

- No! Solubility is a common misconception given the well-known Milk of Magnesia™. When mixing magnesium hydroxide, Mg(OH)2, powder with water, insoluble particles are suspended, and overtime, settle without agitation or shaking. This is true with both industrial and pharmaceutical grades.

How does magnesium hydroxide work?

- Well, it honestly depends on the application. As an example, take wastewater treatment. Magnesium hydroxide, Mg(OH)2, provides an alkalinity source and a pH buffer to neutralize any acidic byproduct or waste. By doing this, the wastewater stream maintains an appropriate pH range. It also provides magnesium as a nutrient for microorganisms, allowing for the biologic decomposition of organic waste. On the other hand, an ultra-high purity grade is used in natural deodorants to help eliminate the underlying cause of odor (microbes and bacteria) on the surface of the skin and attached to hair follicles.

How is magnesium hydroxide made?

Again, it depends. This time on which type. Natural magnesium hydroxide, Mg(OH)2, occurs as the mineral brucite and is mined as such. Brucite is quite rare but can be beneficial in given applications due to its high magnesium content. The mineral can be ground into various particle sizes and used as a powder or made into a slurry.


- Another commonly produced variety is synthetic magnesium hydroxide, Mg(OH)2. The process precipitates magnesium chloride (MgCl2) from seawater (or brine) and combines it with calcium oxide (CaO). The chloride dissolves during hydration and the hydroxides of magnesium and calcium remain. Because it is heavier, the Mg(OH)2 settles out of suspension first, and then it is harvested. The Mg(OH)2 dissociates to its oxide after calcining. The oxide then reacts with the water to produce a hydroxide slurry.


-Finally, rehydrating magnesium oxide, MgO, is a complex process. Mineral experts have been trying to perfect it for decades with various proprietary production plans. Basically, the ideal magnesia (based on % content and impurities) is ground and calcined until disassociated. While closely monitoring all environmental and external conditions, the calcined material is cooled, milled, and chemically hydrated using a multi-step hydration process involving dissolution and diffusion.

What does magnesium hydroxide do in deodorant, and is it safe?

- Magnesium hydroxide, Mg(OH)2, helps get rid of odors without penetrating the dermis or clogging pores and sweat ducts. It is entirely safe. The FDA determined that Mg(OH)2 is Generally Regarded as Safe (GRAS) as in the Code of Federal Regulations (CITE: 21CFR184.1428). Many argue that it is safer than traditional aluminum-based deodorant because it does not absorb into the skin. The Mg(OH)2 is less irritating than baking soda or sodium bicarbonate because unlike baking soda, Mg(OH)2 does not strip the skin of its natural moisture barrier. Ultimately, it balances the body's natural pH while killing bacteria without irritating the skin.

Why is magnesium hydroxide, often called milk of magnesia?

- Milk of Magnesia™ is a pharmaceutical brand name of magnesium hydroxide that is known to provide relief from increased stomach acid while helping to induce bowel movements.  It is called such based on its white milky texture due to the suspension of the insoluble powder.   

bottom of page