If you've ever turned a skincare bottle around and scanned the ingredients list, you've almost certainly seen citric acid somewhere near the bottom. It sounds slightly alarming — acid, after all — but it is one of the most common and best-understood ingredients in modern cosmetics. It does two very different jobs depending on how much of it is in the formula, and understanding which job it's doing will change how you read a label.
So, what actually is citric acid?
Citric acid is a weak organic acid that occurs naturally in citrus fruits — lemons, limes, oranges and grapefruits — and it belongs to the family of alpha-hydroxy acids (AHAs), alongside glycolic acid, lactic acid and malic acid. In nature it's also a normal part of human metabolism: citric acid sits at the heart of the Krebs cycle, the process your cells use to turn food into energy. So it isn't a foreign substance your skin has never encountered.
In cosmetics, the citric acid you find in a bottle is usually produced commercially by fermenting carbohydrates rather than squeezed from fruit, which keeps it consistent and cost-effective. On an ingredients list you'll see it written simply as Citric Acid, sometimes with its chemical name, 2-hydroxy-1,2,3-propanetricarboxylic acid.
Here's the important bit: concentration and context decide what citric acid does.
- At low levels, it works as a pH adjuster and buffering agent. Every skincare formula has an ideal pH — often around 4.5 to 5.5 to match skin's natural acid mantle — and citric acid is used to nudge a formula into that range and hold it there.
- At higher levels, it behaves like a true AHA exfoliant, loosening the bonds between dead surface cells so they shed more readily.
It's also a chelating agent, meaning it binds to trace metal ions in water that would otherwise degrade a formula or destabilise its preservatives. That's a quiet, unglamorous job, but it makes the actives in the rest of the bottle work properly and last longer.
The benefits of citric acid in skincare
Gentle chemical exfoliation
As an AHA, citric acid helps dissolve the "glue" — technically, calcium ions in the intercellular bonds — that holds dead cells to the surface of your skin. The result is a smoother, more even texture and a brighter, less dull-looking complexion. It is generally considered one of the milder AHAs, which makes it a sensible entry point if stronger acids like glycolic acid have irritated you in the past.
Supporting cell turnover
By encouraging dead cells to shed, citric acid indirectly supports the skin's natural renewal cycle. Over time, that can help soften the appearance of fine lines and improve overall tone. It's a supporting player rather than a headline wrinkle treatment, but it contributes to the resurfacing effect of a well-built formula.
Antioxidant support
Citric acid has mild antioxidant properties, helping to defend against free radical damage from pollution, UV exposure and other environmental stressors. It's not in the same league as vitamin C for antioxidant punch, but it adds a layer of protection — and, crucially, it helps other antioxidants in a formula stay effective by chelating the metal ions that would otherwise cause them to oxidise.
pH balance and formula stability
This is citric acid's most common role, and arguably its most valuable. Keeping a product at a skin-friendly pH means the actives — retinol, vitamin C, salicylic acid — remain stable and effective, and it means the product is less likely to disrupt your skin barrier. It also lets preservative systems work properly, which keeps your product safe to use over its shelf life.
A mild astringent effect
Citric acid has a gentle astringent quality, which can help manage excess oil and contribute to clearer-looking skin — particularly useful for oily or blemish-prone types. It may also help discourage the conditions in which spots form, though it is not an acne treatment in its own right.
A word of caution
Because it is an acid, tolerance matters. If citric acid appears high on an ingredients list, you're dealing with an exfoliating product and should introduce it gradually rather than using it daily from day one. Daily sunscreen is non-negotiable when using any AHA, including citric acid, because exfoliated skin is more vulnerable to UV damage. And if you have sensitive or compromised skin, patch test first.
Which REFORM Skincare products contain citric acid?
REFORM Skincare uses citric acid across its range in both capacities — as a genuine exfoliating active in some products, and as a pH adjuster and stabiliser in others. Here's where you'll find it in the UK range:
| Product | Citric acid's role |
|---|---|
| Repair & Renew Gel | Listed as a key active — a mild AHA providing surface exfoliation, contributing to brightness and smoothness, and enhancing the effectiveness of the other exfoliating ingredients in the formula. |
| Gentle Hydrating Crème Cleanser | pH adjuster, helping maintain the formula at an optimal pH for skin compatibility. |
| Intensive Moisturiser | pH adjuster, balancing the formula. |
| Retinol 1% Crème | pH adjuster, maintaining a skin-friendly balance alongside tetrasodium EDTA. |
| SPF 30 Mineral Sunscreen | Maintains the optimal pH of the formula, alongside sodium phytate as a stabiliser. |
The Repair & Renew Gel is the product where citric acid is doing real exfoliating work. If you want the visible resurfacing benefits — smoother texture, brighter tone, clearer-looking skin — that's the one to start with. The others contain citric acid in a supporting role: it's there to keep the formula balanced, stable and skin-compatible rather than to peel your face.
That distinction is worth holding on to. Seeing citric acid on a moisturiser's label doesn't mean you're applying an exfoliant — it usually means the formulator has used it to get the pH exactly where it needs to be. Conversely, seeing it called out as a named active in a resurfacing product tells you it's there in a meaningful concentration.
How to get the most from it
If you're building citric acid into your routine, keep it simple. Use an exfoliating product such as the Repair & Renew Gel two or three evenings a week to begin with, building up only if your skin stays comfortable. Don't stack it with other strong acids on the same night — alternate with retinol rather than layering them, or you risk over-exfoliating and compromising your barrier. Follow with a hydrating moisturiser, and wear SPF every single morning.
Used sensibly, citric acid is a genuinely useful ingredient: mild enough to suit most skin types, effective enough to make a visible difference to texture and radiance, and valuable behind the scenes in almost everything else you own. It's proof that the least glamorous line on an ingredients list is often doing the most work.
