Niacinamide and Acids Can Share a Routine

In everyday use, acids such as glycolic, lactic and salicylic acid can share a routine with niacinamide. On acid days, keep using niacinamide as usual. You may have heard that niacinamide has to go on acid days, or that you need to wait 20 to 30 minutes before layering it. The story goes that the acid turns niacinamide into niacin and flushes your face, and that their mismatched pH cancels both. The flushing claim usually points back to a heated lab experiment from 1962, and the "cancels out" one leaves out that skin brings its own pH back.

Where does the niacin story come from?

Niacinamide, a form of vitamin B3, can turn into niacin (nicotinic acid) under the right conditions. The reaction was measured carefully in 1962 (Finholt & Higuchi, 1962). To track its speed at all, the researchers had to heat the solution well beyond room temperature; at ordinary temperatures it was too slow to follow.

In the same study, the conversion ran slowest in the mildly acidic to neutral range, exactly where skin and skincare live. Niacinamide turns into niacin quickly only with strong acid or base, high heat and long exposure, conditions found in a lab rather than a bathroom.

Does niacinamide convert on your skin?

A product on your face sits near body temperature, and the next layer goes on within minutes. Skincare acids sit around pH 3 to 4 and don't linger. A few minutes at body temperature is unlikely to convert a meaningful amount of niacinamide. Niacinamide is known to be stable across a broad pH range and well tolerated on skin (Wohlrab & Kreft, 2014).

The acid keeps working too. Glycolic, lactic and salicylic acids work through their free-acid form, which rises as pH falls (Kornhauser et al., 2010), and there is little reason to think a layer of niacinamide switches that off. Skin's surface sits, on average, below pH 5 (Lambers et al., 2006), and a brief disturbance is known to settle back over time.

How does the niacin flush happen?

The fear of a red face is the niacin flush, a real response in which nicotinic acid widens blood vessels. The niacin flush is known mainly as a reaction to taking nicotinic acid by mouth. On skin at body temperature, there is little reason to expect much nicotinic acid to form at all.

Layer niacinamide straight onto a fresh acid and you might feel a brief sting or warmth. That is known as ordinary, short-lived irritation from stacking actives, not a sign of niacinamide "becoming niacin."

So what's actually worth watching for?

You can set down the worry that these two ruin each other. When you use niacinamide with acids, avoid stacking too many strong actives at once. Several strong actives together add up the load your barrier carries; a quick self-check can show when a routine has crossed that line. Niacinamide is known to support the barrier (Wohlrab & Kreft, 2014).

You'll often read advice to wait 20 to 30 minutes after an acid before niacinamide. But since a meaningful conversion within minutes at body temperature is unlikely, there's no need to wait that long. If your skin runs sensitive and the sting bothers you, wait a minute or two, or split the two between morning and night.

So: no need to add steps to keep them apart

Niacinamide converts to niacin quickly only under strong acid or base and high heat (Finholt & Higuchi, 1962), and skin's surface sits on average below pH 5 (Lambers et al., 2006). There is no reason to add steps to keep apart two things that were never at war. For why actives can be held together at the right pH, see why well-made formulas hold actives together. If it stings, split the two between morning and night or take one active out.

One step for today

• On acid days, keep applying niacinamide. Niacinamide converted to niacin quickly only with strong acid or base, high heat and long exposure (Finholt & Higuchi, 1962). If it puts your mind at ease, wait a minute or two after the acid, then layer it. If redness lasts for days after applying, see a dermatologist.
• If something stings, take one active away. Whether stinging comes from a clash or from the number of actives hasn't been tested in a trial. The next day, check whether the same spot stings less. Introduce new pairings one at a time, and if stinging and redness continue after you cut back, see a dermatologist.