Now I love’em both. And whilst there are lots of instances where I combine them, sometimes it’s just not the best way forward. Are you shocked??

Well, let’s explore this!

Firstly, let’s consider their benefits individually.

What is Salicylic acid?

Salicylic acid is derived from willow tree bark and is a beta hydroxy acid. This renders it fat soluble, which gives it an affinity for the t-zone and oily skin in general. It’s the same chemical structure so it won’t surprise you that it’s anti-inflammatory and also anti-bacterial.

Finally, it’s also powerfully comedolytic meaning it breaks down clogged pores. So far, so helpful. We typically use it at a strength from 0.5% - 2%.

In a nutshell: As an oil soluble acid, it has the ability to deep clean the pores by dissolving the dead skin cells and clearing them of any debris that can cause spots, breakouts and blemishes.

What is Azelaic Acid?

It’s a dicarboxylic acid found naturally in grains and is produced by a yeast that lives on our skin.

One of its most profound benefits it that it normalises keratinization. That means it’s one of the most powerful ingredients we have when it comes to acne prevention.

It’s also anti-bacterial and anti-inflammatory, so like salicylic acid, it’s helpful in calming existing blemishes.

In a nutshell - it works on everything from acne to rosacea and perioral dermatitis and is a sensitive skin saviour.

So when do I use what?

I tend to use azelaic acid alone in rosacea, rosacea/acne overlap and perioral dermatitis. I also use it in those with very sensitive skin and acne. And it’s a staple in my toolkit for pregnant women who’re breaking out in the first trimester.

I rarely use salicylic acid alone - but I might do in context of mild teen acne with a few blackheads and an oily t-zone.

When do I use them together?

I use them both in someone with acne who can’t tolerate benzoyl peroxide.

I also like them used in combination in someone with marked inflammatory acne or with lots of PIH and congestion.

Final thoughts

These are highly synergistic acids especially in the context of acne. But the combination can be too much for some - in which case I’d suggest starting with azelaic acid. As I mentioned, the exception is an oily t-zone’d teen starting to get a few blackheads - in that case I’d start with salicylic acid.

Ultimately, they share a great mix of benefits which makes them very versatile and essentials in my toolkit.