Vitamin C or niacinamide? What each one is good for

Vitamin C: an antioxidant for sun-damaged skin

Vitamin C (L-ascorbic acid) is an antioxidant, and the skin needs it to make collagen. In a double-blind, half-face study, topical vitamin C improved signs of sun damage, including wrinkling, compared with a vehicle on the other side of the face. A six-month trial of a 5% vitamin C cream found improvements that were visible both clinically and under the microscope.

It suits people whose main concerns are dullness, uneven tone and early sun damage.

Vitamin C is fragile

Pure ascorbic acid breaks down when exposed to light and air; a serum that has turned dark yellow or brown has lost much of its activity. Look for opaque, air-tight packaging, keep the bottle closed and use it up within a few months. More stable derivatives exist, but most of the clinical evidence is for ascorbic acid itself.

Use it in the morning, under sunscreen — the two work well together. Some people find it stings, especially on freshly shaved or irritated skin.

Niacinamide: the even-tempered all-rounder

Niacinamide is a form of vitamin B3. In a 12-week split-face trial, a 5% niacinamide moisturizer improved fine lines, dark spots, red blotchiness and sallowness compared with the vehicle-treated side. Reviews also describe anti-inflammatory effects and support for the skin barrier, partly through increased production of ceramides.

Most skin types tolerate it well, which makes it a good first active for sensitive or acne-prone skin.

More is not better

The clinical evidence for niacinamide is mostly at concentrations of a few percent, up to around 5%. Higher numbers on the label are a marketing figure more than a clinical one, and they are more likely to cause redness or tingling in some people.

Can you use both?

Yes. The old warning that the two cancel each other out came from laboratory conditions that have little to do with a skincare routine. If your skin is reactive, a simple split works: vitamin C in the morning, niacinamide in the evening.

How to choose

If dullness and sun damage bother you most, start with vitamin C in the morning. If redness, oiliness, visible pores or uneven tone are the issue, or your skin is sensitive, start with niacinamide. Introduce one at a time, give it at least eight to twelve weeks, and keep sunscreen as the base — neither ingredient replaces it.