# How to layer skincare: order, waits, and how much to use

Thinnest to thickest, a minute between steps, sunscreen last in the morning. Cleanser, then the low-pH vitamin C serum, then the peptide serum, then the barrier cream, then SPF. At night the vitamin C comes off and retinal goes in, before the cream. That is the whole theory. The rest is amounts.

Canonical: https://existentialcosmetics.com/guides/how-to-layer-skincare

## Why does the order matter?

Three reasons, all chemical. L-ascorbic acid needs a pH of roughly 3.5 or below to be in the form that crosses the stratum corneum, so it goes onto bare, dry skin first, before anything raises the pH at the surface. Peptides are more stable near neutral, so they go after the acid layer has absorbed, not into it. Lipids seal: a barrier cream of ceramides, cholesterol and fatty acids reduces water loss from the surface, which also means anything applied over it is applied onto a seal. Water-based serums first, oil-based creams last, sunscreen on top of all of it.

## What is the morning order?

Four steps and a sunscreen, thinnest to thickest.

- Clean Slate: one or two pumps, lukewarm water, pat dry.
- Bright Side: three or four drops on dry skin. Wait a minute.
- Mixed Signals: one pump. Wait a minute.
- Baby's Bottom: a pea for the face. Very oily skin can skip this in the morning.
- Sunscreen: last, every day, not ours.

## What is the night order?

The vitamin C comes out, retinal goes in, and the cream can move.

- Clean Slate: a second wash if you wore a lot of sunscreen.
- Coming of Age: one pump on dry skin, two or three nights a week to start. Wait a minute.
- Baby's Bottom: over the retinal. Or under it, as a buffer, while your skin adjusts.
- Mixed Signals at night as well? Fine. Before the retinal, with a minute between.

## How long should you wait between layers?

About a minute, and here is the honest footnote: no study in our ledger tested wait times, so the minute is practice, not proof. The reason for it is dilution. A serum applied into a wet layer of the previous serum is applied at half strength into the wrong pH. Once the previous layer has gone from wet to dry, you are done waiting. Cleanser needs no wait beyond patting dry. The barrier cream needs no wait before sunscreen beyond letting it stop feeling wet.

## How much should you use?

The trials used fixed amounts on fixed schedules. Niacinamide was applied twice daily for 12 weeks; the vitamin C, E and ferulic solution was applied daily and had built up protection after four days. More product does not speed the calendar, and more retinal means more irritation on the same calendar.

- Clean Slate: one or two pumps for the face, more for the body.
- Bright Side and Mixed Signals: three or four drops, or one pump, for the whole face.
- Coming of Age: one pump.
- Baby's Bottom: a pea for the face, more for hands, elbows, anywhere dry.

## How do you layer two serums without one cancelling the other?

Vitamin C first, because it has the pH requirement, and peptides after, because they do not. The one real chemistry question in our line is copper and ascorbic acid: copper ions catalyze the oxidation of ascorbic acid in solution, documented in 1969, and nobody has tested whether it matters on skin at cosmetic levels. A minute between the two serums keeps them out of the same wet layer. If you would rather not think about it, Bright Side in the morning and Mixed Signals at night ends the question.

## Where does sunscreen go?

Last, over the barrier cream, every morning. The vitamin C system reduces the oxidative damage ultraviolet light causes and absorbs no ultraviolet light at all; the 2008 human study describes it as complementary to sunscreen, not a replacement. Retinal increases photosensitivity, which makes daytime protection more important. We do not make a sunscreen. Use one you will actually wear.

## Related questions

**Can I skip the wait between steps?**

You can, and the cost is dilution rather than danger. The next serum lands in a wet layer at half strength and, in the case of vitamin C, at the wrong pH. A minute, or until the previous layer stops feeling wet, is enough.

**Does moisturizer go before or after serum?**

After. Serums are water-based and thin; the barrier cream is lipid-based and seals. The one exception is buffering retinal: applying Baby's Bottom before Coming of Age on nights when your skin is adjusting slows the retinal down on purpose.

**Can I use all five products in one day?**

Yes, that is the routine. Four in the morning, three at night, Clean Slate and Baby's Bottom appearing in both. Each product has one job and none of them overlap, which is the point of there being five.

## Sources

1. Murray JC, et al. A topical antioxidant solution containing vitamins C and E stabilized by ferulic acid provides protection for human skin against damage caused by ultraviolet irradiation. J Am Acad Dermatol 2008;59:418-425. (PMID 18603326) https://pubmed.ncbi.nlm.nih.gov/18603326/
2. Bissett DL, Oblong JE, Berge CA. Niacinamide: a B vitamin that improves aging facial skin appearance. Dermatol Surg 2005;31:860-866. (PMID 16029679) https://pubmed.ncbi.nlm.nih.gov/16029679/
3. Hanaki A. Copper-catalyzed oxidation of ascorbic acid. Chem Pharm Bull 1969. (PMID 5347591) https://pubmed.ncbi.nlm.nih.gov/5347591/