When two acid-based treatments land on the same bathroom shelf, the question is rarely about whether either works. Both have cult followings, both promise brighter, smoother skin, and both contain lactic acid at the forefront of their formulation. What matters is which one actually fits into a routine built around dry, reactive, easily-flushed skin, and which one is worth the money once you factor in Australian retail mark-ups and shipping.
My skin is the sort that protests at the first hint of fragrance, breaks out at the thought of a foaming cleanser, and goes tight and papery if I so much as look at a clay mask. Eczema has been a quiet companion on my neck and around my eyes for years, which means most exfoliants are off the table unless they are genuinely gentle. I have been rotating Good Genes and the REN Ready Steady Glow Tonic for several months now, testing each on its own and layered, and there are real differences worth unpacking for anyone shopping from Sydney, Melbourne, or anywhere in between.
If you are newer to acid tonics and want a broader primer on layering, I keep a running guide on The Caryl Edit that explains how I build a routine around barrier repair. For a different perspective on lightweight formulas, this Guardian Watsons sunscreen review is a useful read on how texture shapes everyday wearability.
The headline ingredient in Sunday Riley Good Genes is lactic acid, listed at a relatively high concentration that the brand estimates sits somewhere around the five-to-eight percent mark, though the exact figure is not disclosed on the packaging. It is paired with licorice root, lemongrass, and a cocktail of soothing extracts that help buffer the sting. The formula is technically a serum rather than a toner, and it carries a creamy, almost oil-like slip once it touches the skin.
The REN Ready Steady Glow Daily AHA Tonic relies on lactic acid as well, but at a lower percentage, and it adds willow bark extract, which behaves like a gentle BHA on the surface. The base is watery and alcohol-free, with a formulation that uses ingredients like salicin and a blend of fruit-derived acids to keep the exfoliation measured. There is also a small amount of phytic acid, which helps with tone over time.
In a side-by-side, Good Genes feels like the heavyweight of the two. The lactic acid concentration is meaningfully higher, and the supporting cast is richer, with more emollient ingredients. The REN tonic reads as the gentler daily option, the kind of thing you could realistically use every other morning if your skin prefers slow-and-steady exfoliation rather than a stronger weekly push.
Good Genes pours out as a pale, slightly golden serum. It has a noticeable herbal scent that comes from the lemongrass and the essential-oil blend the brand uses to scent the formula. On the skin, it spreads easily and leaves a soft, slightly tacky finish before sinking in. Over makeup or under moisturiser, it layers without pilling in my experience, though it is not invisible if you apply too much.
The REN Ready Steady Glow Tonic is a clear liquid that behaves exactly like a traditional toner. It has a faint, clean scent that fades within seconds. On application, it absorbs almost immediately and leaves no residue, which makes it a comfortable choice in humid Brisbane summers when heavier serums can feel suffocating. On cooler Melbourne mornings where the air is dry and central heating has stripped the skin overnight, the lighter texture still feels appropriate, but it does not provide the cushioning that Good Genes manages on its own.
Neither product burns on application for me, which is notable given my reactive skin. The REN tonic gives a very slight tingle in areas where my barrier is slightly compromised, particularly across the cheeks. It passes within a minute. Good Genes is mostly comfortable, with the same faint tingle in the same areas, though it tends to feel a touch warmer on first contact.
Over six weeks of alternating nights, both products delivered on the smoothness and brightness front. Texture across my forehead and the area around my nose looked more refined, and the post-inflammatory marks from a winter eczema flare around my jaw faded faster than they normally would. What separated them was how my skin felt the morning after.
Good Genes, used two to three nights a week, left my skin feeling plumped and cushioned. The emollient ingredients in the serum seem to soften the lactic acid's drying potential, and I rarely needed to layer anything heavy on top. On nights when I used it instead of moisturiser, my skin still felt comfortable by morning. For anyone whose skin is barrier-compromised or living through a Melbourne winter where the temperature can swing fifteen degrees in a single day, this cushioning matters.
The REN tonic, used most mornings on a cotton pad, gave a more gradual improvement. The tone of my skin looked more even, particularly across the cheeks, and the willow bark extract seemed to help with the small congestion I sometimes get around my hairline. It is not a substitute for the heavier serum, but it complements one well. The one place I would be cautious is if your skin is mid-flare. Even gentle lactic acid can sting when the barrier is genuinely compromised, and during those weeks I skip both products entirely and reach for a plain lipid cream instead.
Pricing is where these two products diverge sharply, and where Australian shopping habits start to matter. Good Genes retails through Mecca and Sephora in Australia, with the 30ml size sitting around the AUD $115 mark and the 50ml closer to $165. It is not a cheap product, and it is not one you will find at Chemist Warehouse or Priceline, which matters if you prefer to browse in person or redeem loyalty points at the big chains.
The REN Ready Steady Glow Tonic is far easier to find locally. Mecca stocks it, as does Adore Beauty, and a handful of Priceline and Chemist Warehouse locations have carried the 100ml bottle at sale price. Expect to pay around AUD $52 for the standard size, and significantly less during one of the recurring 25-percent-off promotions that Adore Beauty runs through the year. For Australian shoppers who are used to waiting for a stock-friendly sale or who keep an eye on the Mecca member price drops, REN is the easier financial commitment.
There is also a regulatory point worth noting. The Therapeutic Goods Administration regulates cosmetic claims in Australia, and both brands stay within those boundaries. More practically, the Australian standard for sunscreen and UV protection is among the strictest in the world, and using an AHA at night in a country where the UV index regularly climbs past eleven in summer means daytime SPF is non-negotiable. Any acid tonic, including these two, makes skin more photosensitive, so they belong firmly in a nighttime routine.
Where you shop each one also depends on how you prefer to buy. Here is how I split my own purchasing:
Neither product is a mistake, but they serve slightly different roles. Good Genes is the treatment serum, the one I reach for when my skin feels dull, sluggish, or in need of a reset. It is more expensive, more concentrated, and worth it if you are not using any other strong actives and want a noticeable result without a complicated routine. It also suits travel well, since a single 30ml bottle can stretch across two weeks of nightly use.
The REN tonic is the everyday option, light enough to use across seasons and gentle enough to layer under almost anything. It earns its place in my routine on mornings when I want a low-effort step that quietly keeps texture and tone in check.
If you are still deciding, here is how I would describe the fit for each:
For my own routine, the answer ended up being both, used in different slots. The REN sits in the morning after cleansing, the Good Genes takes over on evenings when my skin is asking for something stronger. Both are used with the same caution I apply to any active in a high-UV country, and both are paired with the same barrier-supporting moisturiser that keeps the eczema on my neck from flaring up in the first place.