How to use lactic acid in a skincare routine

What strength should you start with?

A mild 5% formula is one starting option: The Ordinary Lactic Acid 5% + HA is an example. General AHA guidance sets a maximum starting concentration of 10% to 15%; that is a ceiling, not a target you need to reach. Products differ in concentration and base, so follow the directions for your actual formula. A product labelled mild still needs its own directions, because 'mild' is not an instruction manual.125

How to fit lactic acid into your evening routine

1. 1Patch test before using a new product across your face. Follow the brand's testing instructions.
2. 2Apply the lactic acid product at its treatment step, following its directions. The Ordinary places its 5% serum at step 2, Treat, and tells you to avoid the eye area.
3. 3Leave a serum designed to stay on the skin in place. Rinse off a product designed for brief contact at the time stated on its label.
4. 4Start every other evening as general AHA guidance. Gradually increase towards daily use only if your skin tolerates it and the product permits it.
5. 5The next morning, apply SPF 30 or higher sunscreen.

For The Ordinary's 5% serum, apply a small amount to clean skin on the upper forearm, keep the area dry and rinse after 24 hours. Do not use the product if redness, burning, itching, blistering or irritation develops during the test. Its regular directions specify once daily, ideally in the evening.5

Can you use lactic acid with retinol or vitamin C?

Use separate sessions rather than stacking them together. AHA products can be alternated with retinoid creams and vitamin C; vitamin C can occupy the morning routine. The Ordinary specifically lists retinoids, direct vitamin C and other direct acids as combinations to avoid with its 5% serum. Its restrictions also include peptides and niacinamide powder. Check your formula's compatibility directions rather than assuming every lactic acid product has the same rules.235

Does lactic acid suit sensitive or dry skin?

Lactic acid is one of the gentler alpha hydroxy acids, or AHAs: exfoliants that loosen the bonds between dead surface cells. It also acts as a moisturizer, making it useful for rough texture and dryness. Sensitive skin still needs product specific caution. The Ordinary's 5% serum directions say not to use it on sensitive, peeling or compromised skin, despite the product's mild positioning.35

Too much exfoliation can irritate skin and strip away structures that retain water and healthy fats. If The Ordinary's serum causes irritation, rinse it off, stop using it and consult a physician.35

Does evening use remove the need for sunscreen?

No. AHA related sun sensitivity extends beyond the application itself and can last up to a week after you stop. Alongside daily sunscreen, wear protective clothing and limit sun exposure during use and for the following week. Using lactic acid at night does not cancel that daytime precaution.4

What results should you expect?

Lactic acid helps smooth rough texture by encouraging dead surface cells to shed. AHA products can also improve uneven colour and fine lines with regular use. Facial acids take time and consistent use to work; a single application is not the intended routine.23

Chemical peels remove layers of skin and have their own recovery and aftercare requirements. Do not borrow a peel's contact time or recovery expectations for your everyday serum.6