The INKEY List Tranexamic Acid Night Treatment Versus Peter Thomas Roth PRO Strength Niacinamide Discoloration Treatment

In a 24 hour occlusive patch test on 56 subjects, 10% sorbitan isostearate was completely non-irritating. Most formulas use less than 10%.

Because it's a fatty acid ester, it may not be fungal acne safe since the Malassezia yeast can utilize it as a nutrient source.

This is due to how structurally similar it is to what your skin already produces.

Though it is mostly an emollient that helps soften and hydrate skin, it also has some humectant and occlusive action. Humectants help the skin retain moisture while occlusives seal it in, making squalane a triple-threat moisturizer.

Research shows it has antioxidant capabilities that help protect against stressors like UV exposure, specifically UVA induced oxidative stress. This study also found that it supports collagen biosynthesis in human dermal fibroblasts.

No clinical study has reported significant adverse effects and irritation reactions are very rare from this ingredient (even at 100% concentration).

Overall, it's a fantastic ingredient for hydration and is suitable for all skin types.

This depends on the source. Squalane can be derived from both plants and animals. Most squalane used in skincare comes from plants.

Please note: the source of squalane is only known if disclosed by the brand. We recommend reaching out to the brand if you have any questions about their squalane.

Read more about squalene with an "e".

Though squalane is often called an oil, it’s technically not one. It is a hydrocarbon, meaning it is only made of carbon and hydrogen. True oils are triglycerides and made of fatty acids and glycerol.

The term “oil-free” isn’t regulated so companies can define it however they want. Some exclude all oils, while others just avoid mineral oil or comedogenic oils.

Squalane has a comedogenic rating of 1 from the original 1972 study that tested raw ingredients under occlusion on rabbit ears. This system is not standardized or peer-reviewed, and using the raw ingredients is very different from how diluted cosmetic formulations are used on human skin.

A comedogenic rating of 1 means it is "unlikely to clog pores" according to the original rating system.

The overall formula of a product matters more than the individual ingredients on whether or not it will cause clogged pores.

Unlike most brighteners that target tyrosinase (the enzyme that synthesizes melanin), TXA works further upstream. It basically blocks your cells from receiving the signal to produce pigment.

This makes it one of the rare actives that works on three pathways at once:

This makes it effective for treating melasma, post-inflammatory hyperpigmentation (PIH), and sun-induced dark spots.

The most effective cosmetic concentration sits between 2-5% and going higher doesn't boost results.

Side effects are generally mild; occasional irritation, flaking, or dryness have been reported at the start of use. Overall, this ingredient is pretty well tolerated, even by sensitive skin types.

Another perk of this ingredient is that it does not cause photosensitivity, so it's safe to use in the AM and PM.

"Does it actually penetrate?" is the part that gets argued about online and the honest answer from research + clinical trials at this time is "yes, but not easily."

TXA is a small molecule that loves water and carries both a positive and negative charge at the same time. Skin's outer layer is oily so a water-loving molecule like this has a hard time getting through it. Liu et al. 2021 showed that it doesn't really stick around well in the deeper layer where pigment-making cells actually live.

A 2025 paper puts it simply: penetration is poor and it depends heavily on how the product is formulated (Winn et al., J Cosmet Dermatol).

But "poor" isn't "none" and the research is fairly clear that topical TXA does something. A 2026 review that pooled results from multiple studies found it helped with moderate melasma but it didn't outperform hydroquinone. Some individual studies at 3% and 5% went head to head with hydroquinone and help up well.

So the fair takeaway is that it works, it's just slower and fussier about formulation than other actives (how the serum is built matters a lot).

There's real evidence here and it's not just clinic marketing. Reviews of microneedling plus TXA report less pigmentation, less melanin, and less redness (Zhang et al., Chinese Journal of Plastic and Reconstructive Surgery, 2024).

The most useful study compared 42 patients getting microneedling plus TXA against microneedling on its own; the group that got the acid saw much bigger improvement. This suggests the acid is pulling its weight and the needling isn't doing all the work.

Just two things worth flagging here:

Oral TXA also works well for melasma and gets used in clinics. However, it is a systemic drug with clotting-related risks and needs a prescription. Injections into the skin have also been studied with good results.

Neither is something a cosmetic product can do, but they help explain why so much attention goes into getting the topical version right.

You'll also recognize water as that liquid we all need to stay alive. If you see this, drink a glass of water. Remember to stay hydrated!