Can lactic acid be used every night?

What decides whether nightly use makes sense?

Lactic acid is an alpha hydroxy acid, or AHA, that removes dead cells from the skin's surface. The amount of exfoliation depends on the acid concentration, the product's pH, meaning its acidity, and the other ingredients. Two products with the same percentage therefore need not exfoliate equally strongly.34

Consumer safety criteria for lactic acid cosmetics include a concentration of 10% or less, a final pH of at least 3.5, and protection against increased sun sensitivity or directions for daily sun protection. Those conditions are not a nightly schedule: frequency still depends on the product and your skin.4

Lactic acid is one of the gentler AHAs and acts as both an exfoliant and a moisturizer. It can help smooth rough texture, including texture caused by accumulated dead cells. The goal is smoother skin, not a bathroom shelf with its own management structure. Face acids take time and regular use to work; regular use does not have to mean daily exfoliation.35

How should you build an evening routine?

1. 1Read the directions before applying. Check whether the product stays on or needs rinsing, and do not exceed its stated frequency.
2. 2For a product that allows daily use, start less often than nightly as a cautious application of general exfoliation guidance. Increase frequency only if your skin tolerates it.
3. 3Apply gently. Leave on preparations are generally used at night, but follow the specific formula's instructions rather than treating every acid product alike.
4. 4Follow exfoliation with moisturizer to limit dryness.
5. 5Use SPF 30 or higher sunscreen every day. Wear protective clothing and limit sun exposure while using an AHA and for a week after stopping.

What if you mean The Ordinary Lactic Acid 10% + HA?

The Ordinary tells you to apply Lactic Acid 10% + HA once daily, ideally in the evening. It also says contact must be limited in frequency or duration, and advises patch testing first. Apply a small amount to clean skin on the upper forearm, keep the area dry and rinse after 24 hours. Do not use the serum if the test causes redness, burning, itching, blistering or irritation. Avoid the eye area and use only on unbroken skin.1

What else in your routine changes the answer?

Prescription retinoids, retinol and benzoyl peroxide can make skin more sensitive or cause peeling; adding exfoliation can worsen dryness or trigger breakouts. The Ordinary specifically lists retinoids, other direct acids and direct vitamin C among products not to use with its serum. General AHA routines can alternate acids with retinoid creams or vitamin C rather than applying everything together. Keep the rest of the routine simple, rather than giving every bottle a supporting role.1256

When should you skip it or stop?

Do not exfoliate sunburned skin or areas with open cuts or wounds. Avoid aggressive exfoliation if you have a darker skin tone or develop dark marks after irritation. Although lactic acid can suit sensitive skin generally, The Ordinary's 10% serum specifically excludes sensitive, peeling or compromised skin. If that serum causes irritation, rinse it off, stop using it and consult a physician.125

For a lactic acid body product used on keratosis pilaris, the tiny rough bumps often found on arms and thighs, follow its directions exactly. Stop for a few days if skin becomes too dry or irritated. Maintenance often needs treatment only a few times weekly; persistent bumps despite home treatment warrant a dermatologist visit.7