Tranexamic acid: the pigment ingredient that treats both brown and red

If you have ever had a spot heal and leave something behind, you already know the two versions of this problem. Sometimes the mark left behind is brown, and sometimes it is pink or red, and the frustrating part is that most of the products sold for fading marks only address one of the two. Tranexamic acid is the exception, and that is the reason it has become one of the ingredients I mention most often in clinic.

What tranexamic acid actually is

Tranexamic acid is a synthetic version of the amino acid lysine, and it was not invented for skin at all. Its original job, and still its main one in medicine, is to slow bleeding, which it does by blocking the conversion of plasminogen into plasmin. Dermatology came to it sideways, when patients taking it for heavy periods were noticed to have lighter melasma, and the mechanism behind that observation turns out to be the reason the ingredient is so useful on the face.

Plasmin does more than dissolve clots. In skin it drives the release of arachidonic acid and prostaglandins, and it raises vascular endothelial growth factor, which is the signal that tells the skin to build new blood vessels. Prostaglandins stimulate melanocytes to make pigment. Vascular endothelial growth factor keeps the vessels dilated and multiplying. Interrupt plasmin and you quiet both of those signals at once, which is a genuinely unusual thing for a topical ingredient to do.^1,7

Brown marks and red marks are not the same problem

When a spot or a scratch or an eczema patch settles and leaves a brown or grey-brown mark, that is post-inflammatory hyperpigmentation, and the pigment is melanin that the inflammation prompted your melanocytes to produce. It is more common and more persistent in medium and deeper skin tones, and left alone it fades over months rather than weeks.

When the mark left behind is pink, red or purple, that is post-inflammatory erythema, which most people know as post-acne marks. There is no extra pigment involved at all. What you are seeing is dilated and newly formed capillaries in skin that has been inflamed, which is why it blanches slightly if you press on it, and why it shows up most obviously in fair skin.

The distinction matters because it decides what will work. A tyrosinase inhibitor, which is what most brightening serums are, has nothing to act on in a red mark, because there is no pigment there to interrupt. A vascular treatment does nothing for a brown one. This is the most common reason I hear that a brightening serum did not work: not that the product was bad, but that it was aimed at the wrong mark.

Why tranexamic acid works on both

Because plasmin sits upstream of both problems. On the pigment side, tranexamic acid reduces the prostaglandin signalling that tells melanocytes to switch on, so less new melanin is made in the first place; it appears to interfere with tyrosinase activity as well.¹ On the vascular side, it lowers vascular endothelial growth factor and reduces the angiogenesis that keeps a red mark red, and it has a directly anti-inflammatory effect on the mast cells involved in flushing.^1,6

So it is not that tranexamic acid is a stronger brightener than the alternatives. Hydroquinone is more powerful on pigment alone, and I still use it in the right patient. What tranexamic acid does is cover both halves of the mark that acne actually leaves, which for most of my patients is the more useful property, because most faces have some of each.

What the studies actually show

On the brown side, the trial I find most useful is a twelve-week single-blinded randomised study in patients with post-acne hyperpigmentation, which compared a five percent tranexamic acid solution against twenty percent azelaic acid cream, twice daily. Both groups improved significantly, and neither treatment pulled clearly ahead of the other, which is a meaningful result given that azelaic acid is a well-established standard.² A systematic review looking specifically at post-inflammatory hyperpigmentation, and at which route of delivery works best, reaches the same broad conclusion that topical tranexamic acid is effective and well tolerated in this setting.³ There is also a body of work on preventing the pigmentation that follows lasers and other procedures, which is where the oral form has been studied most.^1,4

On the red side the literature is thinner but consistent. The most cited report is a therapeutic pearl in the Journal of the American Academy of Dermatology, in which topical five percent tranexamic acid applied nightly reduced acne-related post-inflammatory erythema within six to eight weeks.⁵ Intradermal and microneedled tranexamic acid have been studied for the same problem, and the reviews of tranexamic acid in rosacea and flushing point in the same direction: this is an ingredient with real vascular effects, not only pigment ones.^1,6

I want to be straight with you about the quality of this evidence. These are small studies, several of them open-label, and much of the work uses solutions compounded from injectable tranexamic acid rather than the cosmetic serums you can buy. It is enough to make me confident recommending it, and not enough to promise you a specific result.

The concentration that matters

Two to five percent is the range where topical tranexamic acid has been shown to do something. Two to three percent appears in the studies of facial dyschromia and in most of the better cosmetic serums; five percent is what the post-acne trials used, both for the brown marks and the red ones.^2,5 Below two percent I would not expect much, and the products that list tranexamic acid last on the ingredient list, well after the fragrance, are relying on the word rather than the molecule.

Going higher does not obviously buy you more, and here is the reason. Tranexamic acid is a small but water-soluble molecule, and it penetrates the skin poorly, so a good deal of what you apply never reaches the level where the pigment and the vessels are. Above five percent the limiting factor is delivery rather than dose, and what you tend to add is stinging.

Which is why formulation matters a great deal with this ingredient, more than the number on the front of the box does. The vehicle it sits in, the pH, whatever the chemist has done to help it through the stratum corneum, and in some newer products an esterified form of the molecule designed to be more lipophilic: those choices are what decide whether a five percent serum behaves like five percent or like nothing at all. It is the one place I will not tell you that the cheapest version is equivalent, because two serums at the same percentage genuinely are not the same product.

It also combines well, which is part of its appeal. Niacinamide works at a different point in the pathway, by blocking the transfer of pigment from the melanocyte into the surrounding skin cells, and kojic acid inhibits tyrosinase directly, so the three of them together address pigment production, pigment transfer and the signalling that starts it, without adding much irritation. Several of the serums with the best data behind them are exactly that combination, and it is a sensible one to look for on a label.

How to use it, and when to expect something

Once or twice a day, on clean skin, before your moisturiser. It is a mild ingredient by the standards of pigment treatment, so it layers comfortably with niacinamide, kojic acid, azelaic acid, and a retinoid at night, and unlike hydroquinone there is no course to finish and no need to cycle off it. If you are treating red marks specifically, the trials applied it at night.

Give it twelve weeks before you decide. Marks like these fade slowly enough that the honest way to judge progress is a photograph in the same light every few weeks rather than the mirror, which will tell you whatever your mood tells it to. And none of it holds without daily sunscreen, because ultraviolet and visible light will re-darken a fading mark faster than any serum can lighten it. If you are treating pigment without photoprotection, you are paying for a serum to undo what the morning is doing.

What it will not do

Tranexamic acid will not clear active acne, and if spots are still forming then new marks will keep arriving faster than the old ones fade, so the acne is the thing to treat first. It will not lift an old, deep-seated brown patch on its own; that is where a proper evaluation and possibly a prescription belong. And the oral form, which is more effective than anything topical in selected patients with melasma, is a medication that requires screening for clotting risk and a prescription, so it is a conversation with your dermatologist and not something to source online.¹

My hope is that this saves you from the specific disappointment of buying the wrong thing twice. Look at the mark and name it: if it is brown, if it is red, or, most likely, if you have some of each. Then you know why this particular ingredient keeps coming up.

References

1. Chen T, Xue J, Wang Q. Tranexamic acid for the treatment of hyperpigmentation and telangiectatic disorders other than melasma: an update. Clin Cosmet Investig Dermatol. 2024;17:2151–2163. doi:10.2147/CCID.S479411
2. Sobhan M, Talebi-Ghane E, Poostiyan E. A comparative study of 20% azelaic acid cream versus 5% tranexamic acid solution for the treatment of postinflammatory hyperpigmentation in patients with acne vulgaris: a single-blinded randomized clinical trial. J Res Med Sci. 2023;28(1). doi:10.4103/jrms.jrms_443_22
3. Alsharif SH, Alghamdi AS, Alwayel ZA, et al. Efficacy and best mode of delivery for tranexamic acid in post-inflammatory hyperpigmentation: a systematic review. Clin Cosmet Investig Dermatol. 2022;15:2873–2882.
4. Lindgren AL, Austin AH, Welsh KM. The use of tranexamic acid to prevent and treat post-inflammatory hyperpigmentation. J Drugs Dermatol. 2021;20(3):344–345.
5. Jakhar D, Kaur I. Topical 5% tranexamic acid for acne-related postinflammatory erythema. J Am Acad Dermatol. 2020;82(6):e187–e188. doi:10.1016/j.jaad.2019.09.074
6. Zhang J, Gu D, Yan Y, et al. Potential role of tranexamic acid in rosacea treatment: conquering flushing beyond melasma. Clin Cosmet Investig Dermatol. 2024;17:1405–1412.
7. Maeda K, Naganuma M. Topical trans-4-aminomethylcyclohexanecarboxylic acid prevents ultraviolet radiation-induced pigmentation. J Photochem Photobiol B. 1998;47(2–3):136–141.

A note: not every mark left behind by acne is what it appears to be, and pigment on the face can have causes that look similar and are treated very differently. This article is general education, not medical advice, and oral tranexamic acid in particular requires medical supervision. Please have facial pigment examined in person by a board-certified dermatologist before treating it.