Anti-dandruff shampoo is becoming more popular, as more consumers are afflicted by dandruff, but many consumers ask us whether there’s legitimate science backing this category of products or if it’s just a marketing gimmick.
In this article we’ll review medical research on what causes dandruff, whether the leading anti-dandruff shampoo brands are likely to be effective based on their active ingredients, and highlight some natural dandruff alternatives with safer formulations than commercial products.
What Causes Dandruff?
Dandruff is a condition caused when seborrheic dermatitis affects skin on the scalp. Medical research documents that this skin condition that can affect any other part of the body; it’s just called “dandruff” when it affects the scalp. It tends to be more noticeable on the scalp because the flaky dry skin can get caught in hair.
As the linked research review details, one of the main causes of dandruff is an overgrowth of a specific type of yeast on the skin called Malassezia. This yeast is a natural part of the skin ecosystem; it’s only a problem when its numbers increase beyond normal limits.
The strength of a patient’s immune system and their genetics are also reported as factors which can increase likelihood of dandruff.
Given that dandruff is caused by localized inflammation and an overgrowth of a specific type of yeast, logical solutions are anti-inflammatory compounds which have an antifungal effect.
Which Compounds Reduce Dandruff?
A medical review of compounds used to treat dandruff, published in the Indian Journal of Dermatology, highlighted some of the research-backed treatments.
Selenium sulfide is a topical antifungal medication which is proven in medical research to reduce levels of the yeast which causes dandruff. It’s the active ingredient in many popular dandruff shampoo formulations like CVS Health Maximum Strength Dandruff Shampoo and Selsun Blue Medicated Antidandruff Shampoo.
As documented in the linked research study, selenium sulfide not only reduces levels of yeast on the scalp which cause dandruff, but also is proven to reduce cell turnover, which is a secondary benefit which can further reduce dandruff.
Pyrithione zinc is another ingredient which is proven to reduce dandruff when included in a shampoo formulation. This is the active ingredient in Head & Shoulders Classic Clean Dandruff Shampoo.
A medical trial from 1985 proved that pyrithione zinc shampoo reduced dandruff levels over time. The researchers also noted that there was a reduction in the level of various microorganisms on the scalp with use of the zinc shampoo.
A more recent medical study analyzed why pyrithione zinc was so effective against dandruff. It appears to have three mechanisms of action against the yeast which causes dandruff: it increases cellular zinc levels in the scalp, inhibits mitochondrial function of the yeast, and makes the scalp environment less favorable to growth of the yeast.
From the available research we can conclude that anti-dandruff shampoo does actually work, but there are some health considerations to keep in mind when choosing commercial anti-dandruff shampoo products.
Questionable Additive Ingredients
While most over-the-counter (OTC) anti-dandruff shampoo products do contain effective active ingredients, they also contain questionable additive ingredients which may be unsafe.
The Head & Shoulders anti-dandruff shampoo mentioned in the previous section is a great example. It contains pyrithione zinc as an effective active ingredient, but it also contains two separate synthetic dyes: Blue 1 and Red 33.
We know from medical research that artificial dyes contain neurotoxic chemicals which aggravate mental health issues, and while the risk is lower for topical products like shampoo than for ingestible products like processed food, we still believe the risk is too high to recommend these products. We recommend avoiding artificial dyes entirely, and we don’t understand why a product formulated for sensitive skin would contain ingredients that can aggravate skin.
Head & Shoulders anti-dandruff shampoo also contains fragrance, which encompasses a broad category of compounds, some of which have proven to be harmful to human health in medical studies. Unless the manufacturer lists which specific fragrance chemicals were used (Head & Shoulders does not), we can’t assess their safety, which is why we recommend avoiding all personal care products containing fragrance.
The Head & Shoulders anti-dandruff shampoo also contains a harsh preservative ingredient called methylisothiazolinone, which has proven risks in medical data at concentrations as low as 16 parts per million (ppm). The concentration in the anti-dandruff shampoo product may be below that level, but the manufacturer doesn’t list the concentration so we don’t know. We generally don’t see the need for preservatives this harsh in products as simple as shampoo.
The Head & Shoulders product is just an illustrative example; we’ve found questionable additive ingredients in nearly every commercial anti-dandruff shampoo we’ve reviewed, which is why we don’t recommend any commercial anti-dandruff shampoo. The manufacturers seem to care more about efficacy than safety, and we only recommend products that prioritize both.
Natural Alternatives for Dandruff
Coconut oil may be an effective natural anti-dandruff treatment. A medical review of coconut oil’s effect on the scalp, published in the Scientific Reports journal in 2021, found that topical coconut oil application increased the levels of healthy bacteria in the scalp (Malassezia globosa), and reduced levels of harmful bacteria associated with dandruff formation (Malassezia restricta).
The study authors noted that coconut oil application also increased skin hydration on the scalp, which has an anti-dandruff effect.
We recommend unrefined coconut oil, sometimes referred to as “virgin” coconut oil, applied topically after a shower. It’s best to apply coconut oil to the scalp and leave it in to absorb, because the effects are longer-lasting and because coconut oil can congeal and clog shower drains.
Shampoo products containing fireweed (Epilobium angustifolium) extract are another promising natural alternative for treating dandruff.
A clinical trial found that fireweed extract at a concentration of 1.5% in a shampoo formulation reduced dandruff by over 50%. Sebum (natural oils on the scalp) production also decreased by 67%, and the researchers concluded that this botanical extract offered “a new innovative approach to dandruff reduction.”
Our general guidance is that trying natural compounds first seems logical for cosmetic issues like dandruff, since commercial products have potentially harmful additive ingredients.
