Is lactic acid an enzyme in serums?

What does lactic acid actually do?

Lactic acid helps loosen the substances holding surface skin cells together, allowing old cells to shed. That is chemical exfoliation: the product encourages shedding rather than physically scrubbing cells away. Regular AHA use can improve the appearance of uneven texture and color. Lactic acid also helps skin retain moisture, so exfoliation is not its only job.13

Finding lactic acid on an ingredient list does not automatically mean the serum is intended to exfoliate. AHAs are sometimes included to adjust pH, meaning how acidic or alkaline a formula is. Products containing AHAs are marketed for texture, tone and fine lines, which gives the front of a bottle plenty to talk about. Read the product's purpose and directions as well as its ingredient list.4

How strong is a lactic acid serum?

The amount of exfoliation depends on the acid's concentration, the formula's pH and the other ingredients. A percentage alone cannot tell you how strongly a serum will exfoliate. Consumer safety criteria for glycolic and lactic acid products include an AHA concentration of 10 percent or less, a final pH of at least 3.5, and either protection against increased sun sensitivity or directions for daily sun protection. Those conditions belong together; the percentage is not the whole safety check.4

Lactic acid is one of the gentler AHAs and can be a useful option for rough texture or sensitive skin. Gentler does not mean irritation is impossible. Sensitive skin can sting or burn after product use, and excessive exfoliation can leave skin red and irritated. Choose the formula and frequency with that in mind rather than treating the ingredient's reputation as permission to use more.25

How should you use a lactic acid serum?

1. 1Read the serum's directions and warnings first. Follow its application instructions rather than borrowing the contact time or rinse instructions from a chemical peel.
2. 2For a product intended to stay on the skin, nighttime application is general AHA guidance. Follow the label's frequency; stronger exfoliation generally needs less frequent use.
3. 3Apply moisturizer after exfoliating. Exfoliation can be drying even when the exfoliating ingredient also has moisturizing properties.
4. 4Use SPF 30 or higher sunscreen every day. Wear protective clothing and limit sun exposure during AHA use and for a week after stopping.

Expect improvement with consistent use, not a complete texture change after one application. Regular use matters more than an elaborate routine, despite skincare's talent for creating extra homework. Facial acids take time to work. Professional AHA peels can gradually improve texture over a few months, but that is a different treatment from a home serum, so do not use a peel timetable as a serum deadline.23

What should you avoid?

Consider your existing routine before adding lactic acid. Prescription retinoids, retinol and benzoyl peroxide can make skin more sensitive or cause peeling; adding exfoliation can worsen dryness. General AHA guidance allows alternating with retinoid creams or vitamin C rather than using every active together. Never exfoliate sunburned skin or skin with open cuts or wounds. Avoid aggressive exfoliation if you develop dark marks after irritation, particularly with darker skin tones.35

Stop exfoliating if your skin becomes red or irritated rather than increasing use to force a result. Burning, rash, swelling and blisters are reported reactions to AHA products, not signs to pursue. A dermatologist can help decide whether exfoliation suits your skin if you are unsure or have questions about using it.45