Azelaic acid vs salicylic acid: which is best for clearing up blemishes?

Ever since general skincare geekery taught us how to pronounce the stuff, salicylic acid has been up there as one of our favourite blemish-busters, championed by dermatologists and revered for its practically 100 per cent success rate at shrinking spots and minimising oiliness, with barely any side-effects or irritation.

But the past few years have seen the rise and rise of (apparent) upstart azelaic acid, said by some to be even more effective at subduing, preventing and regulating breakouts and their after-effects. Cosmetic dermatologist Dr Sam Bunting, whose YouTube channel features lots of azelaic acid advice, is just one avowed fan, stating she “couldn’t be without it for myself and my patients.”

So, is one of these ‘wonder’ actives really better than the other? Do they work in the same way and if not, might they have slightly different uses? And if you’re going to invest in one, which should it be? With Dr Bunting’s help, we got you all the answers and more.

What is salicylic acid and what does it do?

Salicylic is an exfoliating beta-hydroxy acid (BHA) derived from willow bark. Its unique superpower is that, unlike other exfoliating acids, it’s oil-soluble which means it can travel into the oily environment of a pore and clear it out. 

As Bunting explains, congestion happens when skin cells become stuck to each other inside pores and block them, allowing acne-causing bacteria to proliferate. Salicylic acid prevents and treats this in a number of ways:

• It gets inside the pores and dissolves and exfoliates the cell clumps.
• It’s anti-bacterial, so it fights acne bacteria.
• It’s anti-inflammatory, so it calms and flattens angry blemishes.
• It helps exfoliate some of the pigmented surface cells that can appear in the wake of inflammation.

What is azelaic acid and what does it do?

Azelaic acid is not an exfoliating acid like AHAs or BHA, so it doesn’t peel away dead cells. It’s derived from grains but it’s also produced naturally by our own skin bacteria, which may be, says Bunting, why it’s so skin-compatible and gentle. Despite that, it was until recently only available on prescription. Its quick rise to fame started when it became commercially available in lower concentrations.

“What azelaic does for spots is that it normalises keratinisation, the process where cells travel to the skin surface in good order and therefore regulates skin function,” says Bunting. Unlike salicylic, which removes pore-clogging cells, “Azelaic acid stops skin cells getting stuck together, creating blackheads and bumps, then whiteheads and inflamed spots.” So, similar to retinol, azelaic acid makes confused and misbehaving skin act like healthy, well-behaved skin.

But azelaic acid does other great things as well:

• It fights redness. It’s very anti-inflammatory, which is great in case of acne but even better for rosacea as it dials down skin’s over-reaction to irritants.
• Being anti-irritant and calming, it also treats perioral dermatitis (rash-y irritation around the mouth and chin). In fact, it can “deal with most of the minor irritations we suffer on our skin,” says Bunting.
• It fights hyperpigmentation.  It contains excess melanin so works against post-inflammatory hyperpigmentation that comes from acne. It’s even effective against melasma.
• It’s anti-oxidant, protecting skin.
• It clears up and prevents congestion and spots long-term.

Salicylic acid vs azelaic acid – which one is better?

The answer is: neither – they work in different ways, even when it comes to acne. What you need to know is which to use under which circumstances.

Salicylic acid is best for: Oily skin and acute breakouts

“It’s my go-to for subduing pustules, papules and angry breakouts, as it works fast and reliably to clear these up and calm them,” says Bunting. “If you use salicylic in the morning and partner it overnight with a retinoid to normalise skin function and prevent relapses, you have a really good balanced routine for inflamed acne.”

“But given it’s an exfoliating acid (which means it can also improve skin’s luminosity and texture), it can be irritating for some, as well as drying in some formulations,” she says. “So it’s best for oily or combination skin that’s not too sensitive.”

Salicylic acid is also the best choice for on-the-spot occasional zit-zapping, and because it's easy to formulate with there are lots of products with it in.

Azelaic acid is best for:Long-term calming and managing of acne, particularly for sensitive skin

“If you suffer from perioral dermatitis, rosacea, or any degree of redness in any skin tone, either alongside breakouts or by themselves, then azelaic is the right choice,” says Bunting, who also points out azelaic acid the superior choice (better than salicylic) for treating and preventing the brown marks that blemishes can leave. 

Azelaic is hard to formulate with though, and often comes as a slightly powdery lotion that can pill, which some people don’t get on with.

Azelaic and salicylic acid: are they pregnancy-safe?

Azelaic acid is safe for pregnant and lactating women, even at high concentrations. Salicylic at high concentrations isn’t so Bunting advises pregnant women against even off-the-shelf cosmetic salicylic acid products to be on the safe side. 

Can azelaic and salicylic acid be used together?

They can. “For skin that’s not too sensitive, salicylic and azelaic actually work well together,” says Bunting. “I use this combo for those who need a relatively strong acne treatment but cannot tolerate benzoyl peroxide (which can be irritating).”

It can also be used as a 1-2 with salicylic: “once angry breakouts have been subdued with salicylic acid treatment, you can switch to daily azelaic acid to maintain the results and prevent future breakouts,” says Bunting.

What is a good concentration of salicylic acid or azelaic acid?

• Salicylic acid is “useful for acne between 0.5 per cent and to two per cent,” says Bunting, who likes to err towards two per cent in a stay-on formula, for oily skin in particular. 
• Azelaic acid is helpful “anywhere upwards of five per cent,” says Bunting. The maximum concentration in cosmetics is ten per cent. 

Both should ideally be introduced slowly, to build up resistance and/or discover your skin’s limits. For azelaic acid, which should be used all over rather than to spot-treat, Bunting recommends starting with half a dose every other day for at least two weeks and building up. “It causes some stinging in the very beginning but that’s a sign of your barrier function adjusting, and not a reason to stop using it,” she says.

What ingredients can be combined with salicylic acid and azelaic acid?

For acne, both salicylic and azelaic acid work well in conjunction with a retinoid: “use the acid in the morning (with an SPF on top) and retinoid overnight,” says Bunting.

Redness and discolouration also respond well an azelaic acid-retinoid combo.

Azelaic acid, says Bunting, works synergistically with vitamin C serums and niacinamide so these can be used all together in the morning. However, “initially I would definitely split them up to introduce these actives slowly,” she says.

But you should NOT use these acids alongside benzoyl peroxide, strong AHAs such as glycolic acid, or face scrubs. “You will cause a lot of irritation; just park them,” says Bunting.

Three of the best salicylic acids to try

The spot-clearing serum: Garden of Wisdom Salicylic Acid 2%, £12

Contained in a hydrating no-water base (there is no alcohol, which means this on-the-spot or all-over serum won’t dry skin out), this is one of the gentlest leave-on salicylic gels despite its maximum level of the active ingredient. Nukes individual spots as well as breakouts, or can be used as a gentle overnight peel and hydrator. Its pump dispenser makes for clean, precise dosing.

The skin purifying cleanser: Skingredients Sally Cleanse, £30

Massage this gentle purifying cleanser into skin for a minute, several nights a week, to control oiliness and loosen congestion without stripping skin; the potent two per cent salicylic is assisted by gently exfoliating and hydrating PHA.

The brightening blemish moisturiser: Elf Blemish Breakthrough Calming Water Cream, £12

A quenching water cream (more like a gel – no heaviness) powered by salicylic alongside pimple and PIH-busters zinc PCA, niacinamide at a powerful 4 per cent, and brightening tranexamic acids and n-acetyl glucosamine. A really good moisturiser for oily skins

Three of the best azelaic acids to try

The skin calmer: Skin + Me Brighten & Boost Calming Azelaic Acid Serum, £19.99

Ten per cent azelaic to unblock pores and/or tone down redness, assisted by anti-inflammatory, microbiome- and skin barrier restoring peptides, bisabolol, panthenol and ectoin. An all-round multi-tasking calmer.

The anti-bacterial treatment: Mantle The Treat Clearing Azelaic Acid Treatment, £37.60

A delicate pale pink serum that packs 10% azelaic, calming, hydrating and anti-bacterial fermented dragon blood (that’s a plant), and soothing and antioxidants CBD and lingonberry oils and extracts to gently transform flushing and breakout-prone skin.

The targeted spot gel:Dr Sam’s Flawless Neutralising Gel, £29

Proving that azelaic and salicylic can be safely combined (when formulated by an expert), this two per cent salicylic plus five per cent azelaic is further boosted by 0.5 per cent retinol-like Bakuchiol and conditioning squalane for ultimate irritation-free spot busting.