Citric acid is one of the quiet workhorses of skincare. It's an AHA (alpha hydroxy acid) like glycolic and lactic acid, but you'll rarely see it advertised on the front of a bottle. Instead it hides in the ingredient list of a huge number of products, doing two different jobs depending on how much of it is in the formula. Here's what it actually does, and whether it deserves a more deliberate spot in your routine.
What is citric acid?
Citric acid is an alpha hydroxy acid found naturally in citrus fruits, though the version in your skincare is almost always produced by fermentation rather than squeezed out of lemons. It plays two roles in cosmetics:
- As a pH adjuster. In small amounts, citric acid is used to fine-tune the pH of a formula so the product is stable and its active ingredients work properly[1]. This is why it appears in everything from cleansers to sunscreens; at these concentrations it has no exfoliating effect at all.
- As an exfoliant. At higher concentrations, it behaves like other AHAs, loosening the bonds between dead skin cells so they slough away and reveal fresher skin underneath.
Worth knowing: citric acid has a lower pH (around 2.2) than most other AHAs, so at exfoliating strengths it can be more irritating than glycolic or lactic acid at the same concentration.
What are the skincare benefits of citric acid?
Citric acid is less researched than glycolic acid, so the evidence base is smaller, but here's what the anecdotal and clinical evidence supports:
- Exfoliates the skin: as an AHA, citric acid helps slough off the outermost layer of dead skin cells, revealing a brighter complexion underneath.
- Brightens and evens tone: by boosting cell turnover, it gradually fades dullness and helps soften the look of dark spots and post-blemish marks.
- Increases epidermal thickness: a small study by E. F. Bernstein[2] found citric acid increased the thickness of the living epidermis and improved skin cell turnover, both markers of healthier, more resilient skin.
- Reduces fine lines and wrinkles: through stimulating collagen production and improving turnover, citric acid can soften early signs of aging with continued use.
- Helps prevent breakouts: faster cell turnover means dead skin is less likely to sit around clogging pores, which reduces the raw material for blackheads and blemishes.
Citric acid vs glycolic acid: which should you choose?
For deliberate exfoliation, glycolic acid is usually the better pick. It has a smaller molecule, decades more research, and more predictable results. Citric acid's strength is as a supporting ingredient: it often appears alongside glycolic and lactic acids in multi-acid peels and toners, where it contributes brightening while the others do the heavy lifting.
In other words, you don't need to hunt for a dedicated citric acid product. You almost certainly use it already.
How to use it without irritating your skin
If you're using a product where citric acid is an active exfoliant (a toner, peel or mask rather than a cleanser where it just adjusts pH):
- Start with two evenings a week and build up gradually.
- Don't stack it with other exfoliating acids or retinoids on the same night.
- Patch test first, especially if your skin is sensitive; the low pH makes citric acid more prone to stinging.
- Wear SPF daily. Like all AHAs, citric acid increases sun sensitivity, and skipping sunscreen undoes the brightening you're working for.
And a plea from us: skip the DIY lemon juice trend. Raw citrus on skin is unbuffered, unpredictable and a classic cause of irritation and photosensitive reactions. Formulated products exist for a reason.