Is citric acid helpful for dandruff or scalp irritation?

Many people confuse dandruff with scalp irritation, although they are not the same and do not respond to the same treatments. Dandruff is a condition marked by excessive flaking of the scalp skin, often accompanied by itching. It is common, chronic, and typically associated with the presence of a fungus called Malassezia. Scalp irritation, however, does not always involve fungi; it may stem from allergic reactions, cosmetic product sensitivities, contact dermatitis, or skin conditions such as psoriasis. Understanding this difference matters, because the causes—and therefore the treatments—are not interchangeable.

This leads to a key question: can citric acid, a natural compound found in many fruits and cosmetic products, actually help manage either of these scalp issues?

What is citric acid and why is it used in hair products?

Citric acid is a weak organic acid naturally present in citrus fruits like lemons, oranges, and limes. In hair and skin products, it is commonly used to adjust pH. This means it helps maintain the acidity level of a product, so it stays compatible with the slightly acidic nature of human skin (pH around 5.5). When the scalp's pH is disrupted—by harsh products or environmental stress—problems like dryness, fungal overgrowth, or inflammation can develop. In shampoos, citric acid also contributes to closing the cuticle layer of hair strands, giving them a shinier appearance. Some early laboratory studies have even examined whether it can act directly against fungi linked to dandruff, but this evidence is limited and not yet conclusive.

Does citric acid work against dandruff?

Dandruff is strongly associated with imbalances in the scalp's microbiome, particularly the overgrowth of Malassezia globosa. This fungus breaks down natural scalp oils into compounds that irritate the skin, triggering inflammation and flaking.

In a study published by Mycoses in 2018, researchers tested how organic acids affected Malassezia fungi in lab cultures. Citric acid slightly inhibited the growth of Malassezia restricta but had little to no effect on Malassezia globosa, which is the more dominant species in dandruff cases. It’s important to stress that this was an in vitro study—done outside the human body, in petri dishes. That means its findings do not necessarily translate into real-world effectiveness.

Moreover, a clinical trial referenced in a review by the American Academy of Dermatology found that shampoos with antifungal ingredients like ketoconazole significantly reduced dandruff symptoms over four weeks. Citric acid, included only as a pH adjuster, showed no meaningful antifungal effects in comparison. These results support the idea that while citric acid may create a favorable scalp environment, it cannot be considered an active treatment for dandruff.

What if the problem is irritation, not dandruff?

Scalp irritation can be caused by multiple factors, and fungi are rarely to blame. Some people experience redness, itching, or burning after using certain hair dyes, fragrances, or harsh cleansers. In this context, citric acid has a more complex role.

At low concentrations, citric acid can help maintain a product’s skin-friendly acidity and may reduce the risk of irritation. However, in higher concentrations or in individuals with sensitive skin, it can actually cause irritation itself.

The U.S. Food and Drug Administration (FDA) lists citric acid as "generally recognized as safe" for use in cosmetics, but does not classify it as an active therapeutic agent. A report by the Cosmetic Ingredient Review (CIR) panel also notes that although citric acid is widely used, it can cause mild skin irritation, particularly in leave-on products or when used undiluted. Further supporting this, a 2020 study conducted by the North American Contact Dermatitis Group reviewed over 49,000 patch test results. Citric acid was found to be a minor but consistent cause of positive allergic reactions, especially when combined with fragrances or alcohols. This does not mean citric acid is inherently unsafe, but it emphasizes the need for caution in sensitive individuals.

Why is it important to distinguish between dandruff and irritation?

Most commercial shampoos are designed to treat dandruff because it is a chronic condition. Dandruff usually requires regular use of active ingredients like ketoconazole, zinc pyrithione, or selenium sulfide to control fungal activity and reduce inflammation.

Scalp irritation, however, is typically a reactive issue. Something that flares up temporarily after exposure to a trigger. It is usually managed by discontinuing the irritating product, resting the scalp, and switching to gentler, fragrance-free formulas. Many people misinterpret irritation for dandruff and buy anti-dandruff shampoos unnecessarily, which can actually worsen symptoms.

In that sense, citric acid may have a place in daily-use shampoos that are meant to maintain scalp health. But it is not appropriate to rely on it as a primary solution for either condition.

So, is citric acid helpful?

Citric acid can be helpful in small ways: it adjusts pH, contributes to product stability, and supports a healthy scalp environment. However, it is not a treatment for dandruff nor a soothing agent for irritation. Its benefits are indirect, and in some cases—particularly with sensitive skin—it can contribute to discomfort. The bottom line is this: citric acid is not harmful in most cosmetic formulations, but it should not be confused with an active medical ingredient. If you’re struggling with persistent flaking or irritation, a visit to a dermatologist is the best way to get a proper diagnosis and targeted treatment.

References

U.S. Food and Drug Administration. (2022). Citric Acid. Retrieved from https://www.fda.gov/cosmetics/cosmetic-ingredients/citric-acid

Cosmetic Ingredient Review Expert Panel. (2014). Safety Assessment of Citric Acid, Inorganic Citrate Salts, and Alkyl Citrate Esters as Used in Cosmetics. Retrieved from https://online.personalcarecouncil.org/ctfa-static/online/lists/cir-pdfs/FR682.pdf

Sasseville, D., Fowler Jr, J. F., Taylor, J. S., Maibach, H. I., & DeKoven, J. G. (2021). North American Contact Dermatitis Group Patch Test Results: 2015–2016. Dermatitis, 32(1), 5–17. Retrieved from https://pubmed.ncbi.nlm.nih.gov/33651458/

Wang, V. M. Y., & Lee, M. H. (2020). Antifungal Agents in the Treatment of Seborrheic Dermatitis. Journal of Clinical and Aesthetic Dermatology, 13(8), 32–38. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7451023/

Draelos, Z. D. (2019). Treatment of Dandruff: A Review. Journal of Cosmetic Dermatology, 18(5), 1240–1244. Retrieved from https://pubmed.ncbi.nlm.nih.gov/31069733/