Magnesium hydroxide (Mg(OH)₂) — commonly known as milk of magnesia — is a gentle, multi-functional mineral with a 200-year history in medicine and wellness. Today, it’s a star ingredient in natural cosmetics, offering aluminum-free deodorant action, oil control, and soothing relief for sensitive skin. This Australian formulator’s guide explores the science, benefits, and DIY uses of cosmetic-grade magnesium hydroxide.

What is Magnesium Hydroxide?

White, odourless powder — slightly soluble in water, forming a mildly alkaline suspension (pH ~10). Sourced from brucite mineral or seawater.

Key Properties

• Neutralises acids (odor, sebum)
• Non-irritating — safe for sensitive skin
• Absorbent — controls oil without drying
• Anti-inflammatory — calms redness

Cosmetic Uses of Magnesium Hydroxide

1. Natural Deodorants (Aluminum-Free)

Replaces baking soda & aluminum — neutralises odor without blocking pores.

• Use level: 5–15% in cream/stick
• Texture: Smooth, non-gritty
• Sensitive skin safe

2. Face Masks & Cleansers

Oil-absorbing clay alternative — gentler than kaolin.

• Use: 10–30% in powder masks
• Best for: Oily, acne-prone, sensitive

3. Toothpaste & Oral Care

Mild abrasive + pH buffer — whitens without enamel damage.

4. Soaps & Body Washes

Add 1–3% for mild cleansing and skin-soothing effect.

Other Uses

• Antacid: Neutralises stomach acid
• Laxative: Osmotic effect
• Flame Retardant: Releases water when heated