Structure, Function, Usage, and Benefits of Lactic Acid (Serum) on Your Skin

Structure and Chemistry of Lactic Acid

Lactic Acid (C₃H₆O₃) is an alpha-hydroxy acid (AHA) naturally found in milk and produced by fermentation of sugars. Its structure has a hydroxyl group (–OH) and a carboxylic acid group (–COOH), which makes it water-soluble and able to interact with the skin’s outer layer. The acid group gently breaks the bonds between dead skin cells, while the hydroxyl group attracts water to keep the skin hydrated. This combination helps remove dull, dead cells, promote cell turnover, and reveal smoother, brighter skin.

In skincare, this unique structure allows Lactic Acid to:

• Break down the bonds (desmosomes) between dead skin cells, gently exfoliating the skin.

• Promote cell turnover for fresher, smoother skin.

• Enhance natural moisturizing factors (NMFs), improving hydration while exfoliating.

• Improve absorption of other skincare ingredients.

How Lactic Acid Works on Your Skin

Lactic Acid functions as both an exfoliant and a hydrator.

• As an AHA, it loosens the “glue” holding dead skin cells together, revealing brighter, more even skin underneath.

• Unlike stronger AHAs (like glycolic acid), it has a larger molecular size, which penetrates more slowly and makes it gentler for sensitive skin.

• It also helps stimulate ceramide production, strengthening the skin barrier.

Over time, regular use improves texture, fades dark spots, reduces fine lines, and boosts hydration.

Why Skin Needs Lactic Acid

Skin naturally accumulates dead cells that can cause dullness, clogged pores, and uneven tone. Environmental damage, aging, and hormonal changes can worsen this buildup.

Lactic Acid addresses these issues by:

• Removing surface dullness caused by dead cells.

• Reducing post-inflammatory pigmentation from acne.

• Helping retain moisture by supporting natural hydration.

• Softening rough, dry, or keratinized skin.

Benefits of Lactic Acid on the Skin

• Gentle exfoliation: Improves radiance without harsh peeling.

• Brightens skin tone: Reduces dark spots, acne marks, and uneven pigmentation.

• Hydrates while exfoliating: Retains moisture for a plump, soft texture.

• Anti-aging support: Reduces fine lines and smooths wrinkles.

• Improves product absorption: Prepares skin for serums and moisturizers.

Sources of Lactic Acid for the Skin

Lactic Acid is commonly included in:

• Serums: For targeted exfoliation and hydration.

• Cleansers: Mild daily exfoliation while cleansing.

• Creams and lotions: Ideal for dry or textured skin.

• Peels: Higher concentrations under professional use for deep exfoliation.

How to Safely Use Lactic Acid Serum

Recommended Concentrations:

• 2–5%: Gentle daily exfoliation and hydration.

• 5–10%: Moderate exfoliation, suitable for pigmentation and texture.

• >10%: Professional peels, to be used under dermatologist supervision.

Routine Application:

1. Cleanse: Gentle cleanser to avoid stripping the skin.

2. Apply Lactic Acid Serum: Start 2–3 times per week at night, increase frequency as tolerated.

3. Moisturise: Lock in hydration to prevent dryness.

4. SPF Protection: Daily sunscreen is essential, as exfoliation increases sun sensitivity.

Who Should Use Lactic Acid

• People with dull, dry, or rough skin.

• Those with sensitive skin who cannot tolerate stronger acids like glycolic acid.

• Individuals with mild pigmentation, acne scars, or uneven skin tone.

• People seeking hydration plus exfoliation in one step.

It is safe for most skin types but should be introduced gradually to avoid irritation.