Magnesium Hydroxide
molecular structure · PubChem
AKA: 1309-42-8, Milk of magnesia, Magnesium dihydroxide, Magnesium hydrate, Magnesium hydroxide (Mg(OH)2), Magnesium(II) hydroxide, Phillips magnesia tablets, Magnesium (as hydroxide), Magnesii hydroxidum
Synthetic
Clean
Magnesium Hydroxide is a solution of magnesium hydroxide with antacid and laxative properties. Milk of magnesium exerts its antacid activity in low doses such that all hydroxide ions that enter the stomach are used to neutralize stomach acid. This agent exerts its laxative effect in higher doses so that hydroxide ions are able to move from the stomach to the intestines where they attract and retain water, thereby increasing intestinal movement (peristalsis) and inducing the urge to defecate.
Solubility Practically insoluble in water and in ethanol
Formula
H2MgO2
Mol. Weight
58.32
CAS #
1309-42-8
Form
Powder
State
Dry Powder, Liquid; Pellets or Large Crystals; Liquid; Water or Solvent Wet Solid; Dry Powder; Other Solid
Functions
Absorbent
Buffering
Anti-Inflammatory
Boosts Collagen
Wound Healing
Absorbs excess oil
Maintains optimal pH
Traditional Use
Developed as a modern cosmetic and pharmaceutical ingredient in the 19th-20th centuries. Used industrially as a base and buffering agent; adopted in cosmetics for pH adjustment and as a mild abrasive in some formulations.
Skin Types
●all-skin-types
Best For
General
Pregnancy & Breastfeeding Safe
Yes
The paper trail
🔬Peer-reviewed1 paper →
⚖️Regulatory1 listing →
🛡️Safety-assessed2 reviews →
Counts, not a verdict. A listing isn't a study. The trail, you decide.
Verified Jun 2026
Data: PubChem · CosIng · EWG · CIR