This bestselling US serum is renowned for giving seriously radiant skin, but it’s been reformulated for the UK—how does it compare?

Sunday Riley products often get rave reviews and reach cult status. Good Genes, the brand's iconic exfoliating serum racks up hundreds of 5-star ratings on Amazon and has a loyal following. However, there are two different versions and it's important to know the difference. There's the original Sunday Riley Good Genes All-in-One Lactic Acid Treatment, which is the brand’s US iteration of the Good Genes serum. This skin-brightening treatment has legions of fans stateside, including the likes of Oprah, Drew Barrymore and Helen Mirren no less. However, there's also the Sunday Riley Good Genes Glycolic Acid Treatment - the UK version, which was tweaked by the brand a few years back to adhere to the EU regulations around product formulation. You can only buy the glycolic version in the UK. If you see the lactic acid treatment for sale, I urge you to be careful as it may not be properly advertised.

The UK's glycolic acid serum promises all the same skin-brightening exfoliating benefits, but with an ingredients list that sticks to the EU rules. But is it any good? Ahead, I share my honest review of the cult serum and break down the differences between the UK and the US formulations.

My Honest Sunday Riley Good Genes Glycolic Acid Treatment Review

First impressions

I’ve been a big fan of Sunday Riley skincare for a few years now and I have been through a couple of bottles of the Sunday Riley Good Genes Glycolic Acid Treatment to date—so this review was a pretty easy one for me. (Spoiler: I love it.) For context, I’m 35 and my skin is spot-prone, has some pigmentation and uneven texture, and I have two young kids so I look perpetually tired.

Let’s get into the product itself—the texture of this is delightful. Sunday Riley calls it a treatment rather than a serum - that's down to the fact that you get results that are reminiscent of a mini facial. I also think it's because the texture sits somewhere between a serum and a moisturiser—it’s silky-smooth, creamy and feels surprisingly nourishing on the skin.

And while I always try hard not to let the packaging of a product dictate my impressions of the formula inside, it has to be said that Sunday Riley packaging feels so premium. From the luxurious box that the product is housed in to the heavyweight frosted glass bottle and the pump that disperses the perfect amount of treatment—it feels like a real treat to use.

The formula

Let’s get into the nitty-gritty, shall we? What makes up the Sunday Riley Good Genes Glycolic Acid Treatment and how does this differ from the Good Genes Lactic Acid Treatment that is only meant to be available in the US? The first thing to note is that EU regulations dictate that lactic acid treatments are only permitted with a maximum concentration of 10% and a pH of at least 3.5. The Lactic Acid version of Good Genes boasts a 7% concentration of lactic acid and a pH of 3. So as the pH is too low, the UK version harnesses glycolic acid as its AHA of choice at a level of 7%, with lactic acid salt at 3% (that’s potassium lactate on the ingredients list) and a pH of 3.5.

The crux of it is that both formulas work to gently buff away dead skin cells, exfoliate pores, brighten the surface of the skin, and basically leave your skin brighter than before. The good thing about the UK version, in my opinion, is that glycolic acid has a slightly smaller molecule size than lactic acid which actually means this version penetrates the skin slightly more deeply and helps to regenerate and resurface for even glowier results. The downside, however, is that people can be slightly more reactive to glycolic acid than lactic acid so those of you with sensitive skin should patch test before using this.

The results

Typically, glycolic acid isn’t my AHA of choice. As someone prone to spots, I prefer the gentler nature of lactic acid and generally find it a less irritating option for my skin. However, I have used Sunday Riley Good Genes Glycolic Acid Treatment on and off over the last few years and have never reacted to or found that it has exacerbated breakouts or irritation. In fact, I’d say that it’s actually one of the few skincare products I’ve used that can make a noticeable difference to my skin for the better within days of using it.

If I’ve recently had a bad batch of hormonal acne, my skin is feeling particularly congested or dull, or I’ve noticed an increase in pigmentation caused by spot scarring, then this is the product that I’ll use for an instant complexion pick-me-up. I personally only use it at night due to the high concentration of AHAs (and I make sure to use a facial sunscreen the following day) but I will always wake up to smoother, brighter, more even skin. Honestly, I’ve paid for facials where my skin has looked less impressive afterwards.