Does lactic acid go before or after moisturizer?

The product format decides the order

Lactic acid is an alpha hydroxy acid, an ingredient that helps remove dead cells from the skin's surface. It also helps keep skin hydrated. Those two jobs explain why lactic acid appears in both exfoliating products and moisturizing creams. Use the product's actual directions rather than treating every lactic acid product as interchangeable, because a shared ingredient is not a shared instruction manual.3

How to use a lactic acid mask with moisturizer

1. 1Test a new mask on small areas of skin before using it more widely.
2. 2Gently apply the mask with your fingertips, following its label.
3. 3Leave the mask on only for the time specified. Longer use can cause irritation.
4. 4Wash off the mask as directed, then apply moisturizer.

Avoid adding an exfoliating mask that duplicates acids already in your routine, particularly if you also use retinol. Repeated exfoliating ingredients can trigger dryness and irritation. A mask is an addition to cleansing, moisturizing and sun protection, not a replacement for those steps.1

What if lactic acid is in your moisturizer?

A cream containing lactic acid can combine moisturizing and exfoliating in one product. For example, IPG Pharmaceuticals' ammonium lactate 12% body cream is formulated to hydrate, soften and exfoliate dry, rough skin. A moisturizing cream already fills the moisturizing role, so another cream does not need to be hired just to make the routine look busy.2

That particular cream's label directs application to dry skin twice a day, or as directed by a doctor. Keep it away from eyes, lips and mucous membranes. The label warns that facial use can cause irritation and that application to cracked or scraped skin can cause temporary stinging. These are directions for that body cream, not a schedule for a facial serum.2

Which moisturizer should you use?

If you have acne, look for a moisturizer labeled oil free, noncomedogenic or 'won't clog pores.' These descriptions mean the moisturizer is unlikely to cause acne. Moisturizer is useful when skin feels dry, including during treatment with benzoyl peroxide, salicylic acid or prescription retinoids. Daily moisturizing can help skin tolerate those drying treatments; that does not make adding another exfoliant necessary.4

How often should you use lactic acid?

Follow the frequency and application directions for your particular product. For keratosis pilaris, the rough bumps commonly found on upper arms and thighs, general exfoliation guidance is to start two to three times weekly and increase slowly as tolerated. Improvement can take weeks of consistent treatment. That schedule concerns exfoliation for those bumps; it is not a universal facial serum schedule.5

What if lactic acid stings?

Lactic acid can cause stinging or burning even without a visible rash. A product tolerated on the body can irritate the face, and eyelids are especially sensitive. If lactic acid triggers discomfort, avoid the triggering product and use a moisturizer that does not irritate your skin rather than trying to solve the problem by changing the order.6

Wash off a mask immediately if it causes itching, burning or stinging. See a dermatologist if your skin feels worse after mask use. For the IPG ammonium lactate cream, stop use and contact a doctor if irritation or rash persists. Its label also directs you to avoid unnecessary sun exposure and use sunscreen.12