Selenium sulfide is an antifungal agent used in the treatment of seborrheic dermatitis, pityriasis versicolor, and tinea capitis (scalp ringworm). It’s a non-metallic trace mineral, found naturally in sulfur ore (and Brazil nuts!). It’s required at low doses for a range of cellular processes, including protective antioxidant activity, and thyroid function .
Selenium sulfide shampoos are widely used, and available to buy over-the-counter (OTC) from UK pharmacies. In the United States, the concentration of selenium sulfide in shampoos sold by pharmacies is restricted to 1% – all 2.5% shampoos require a prescription
Quite why it’s deemed OTC safe in Europe but not the USA I don’t know. It seems like such a pointless thing to have to bother a doctor for. But the law is the law…
The most common brand is ‘Selsun 2.5%’, which is massaged into the scalp for 2-3 minutes before rinsing – twice weekly for two weeks to control symptoms. Selenium sulfide shampoos shouldn’t be used on broken or inflamed skin, and so you should consider speaking to your doctor or pharmacist before use .
A brief history of selenium sulfide
Selenium sulfide shampoos were first developed as an alternative to sulfur, as the two are chemically very similar, and sulfur was associated with irritation and poor patient compliance. The chemists Slinger and Hubbard are credited with discovering that a 2.5% suspension had the most therapeutic benefit, with the least absorption .
A 1954 review article published in The Journal of the American Medical Association (JAMA), noted that the use of a selenium sulfide ‘shampoo’ (really just two teaspoons of selenium suspension with soap) was associated with:
‘Within a few weeks remarkable improvement of the seborrhea usually takes place…’
How does selenium sulfide work?
Selenium sulfide is a complex molecule, forming rings of various sizes comprised of selenium and sulfur atoms. It’s not clear how the ingredient exerts an antifungal effect but is known to be effective against the yeasts and fungus commonly associated with scalp conditions (e.g. Malassezia, P. Ovale). A possible mechanism is selenium accumulation, leading to apoptosis (cell death) .
How effective is selenium sulfide?
Selenium sulfide shampoos are widely used as first or second-line treatments in seborrheic dermatitis, pityriasis versicolor, and tinea capitis. As with many antifungal ingredients used in shampoos, there isn’t always strong clinical trial evidence backing their use, clinicians instead relying on experience.
Selenium Sulfide for Seborrheic Dermatitis
In the USA and UK, selenium sulfide shampoos are a first-line alternative to ketoconazole. This recommendation is based on a pivotal systematic review published in 2010, which evaluated the efficacy of ketoconazole and selenium sulfide for seborrheic dermatitis. The study reviewed six high-quality trials, ranging from 20-350 participants, and found that both ingredients were associated with an improvement in scaling, itching, redness, and dandruff .
This is a follow up from an earlier study which found “Both ketoconazole 2% shampoo and selenium sulfide 2.5% shampoo are effective in the treatment of moderate to severe dandruff; however, ketoconazole 2% shampoo appears to be better tolerated.” 
There are other anti-fungal conditions that selenium sulfide is used for. Pityriasis versicolor, for example, is caused by an imbalance of yeast normally found on the skin. Selenium shampoos are recommended to treat this condition by specialist dermatology groups. Studies have found both ketoconazole and selenium sulfide are more effective than placebo . In addition, Tinea capitis (ringworm) is a common fungal infection. Due to an absence of high-quality evidence, treatment guidelines have been agreed by UK and EU specialist groups (BAD, HPA, and ESPD), based on experience and available clinical trials .
Selenium sulfide shampoos are particularly useful for this condition because they are licensed for children over 5 – ketoconazole is licensed from adolescence.
What are the risks?
Selenium sulfide shampoos are associated with a higher incidence of adverse effects than ketoconazole, with the most common reactions being: redness, irritation, burning sensations, dry hair, and blistering (if the shampoo is left on the skin for too long). Importantly, selenium sulfide shampoos have been known to discolor dyed hair, and can discolor metallic jewelry – so should be removed before use .
The US Department of Health’s ‘Report on Carcinogens’ rates selenium sulfide as: ‘reasonably anticipated to be a human carcinogen’. This recommendation is based on high-dose oral animal studies, but the reports note that application of a 2.5% shampoo to mice did not cause any tumor growth after 88 weeks . Selenium sulfide shampoos should not be ingested, and only used in accordance with the recommended dosage instructions.
Shampoos that contain selenium sulfide
Here are the best Selenium Sulfide shampoos we’ve reviewed yet
Vichy Dercos shampoos for oily/dry scalp are a very decent pair of combination shampoos for treating seborrheic dermatitis. It's the first time we've reviewed a Selenium Sulfide/Salicylic Acid shampoo and it's a combination of great promise.
They aren't perfect shampoos though containing fragrance, sulfates, silicones and a few other potential irritants.
If you're looking for a prescription strength formulation available OTC, and you haven't got a particularly sensitive scalp - it's definitely worth checking out.
Selsun Blue was probably the most effective shampoo available OTC once upon a time. These were in the bad old days when Head and Shoulders was the only viable alternative *shudders*.
As its name implies, Selsun Blue is a blue. Very very blue. Even the foam that it creates is blue. The blue coloring is achieved via a food coloring additive. You might want to take care when using this shampoo since the colorant turned my shower basin blue.
There are also one or two ingredients which you may wish to know about. It contains DMDM Hydantoin, a formaldehyde releasing preservative that can irritate the skin and scalp. Also, the foaming agent is Cocamide DEA, which is a coconut oil derivative that is also can also cause contact dermatitis. It’s not sulfate free either.
Its not all bad though. It’s still a decent shampoo for milder cases of dandruff. However it certainly doesn’t pack the punch that 2.5% formulations do.
If you suffer from mild seb derm then its worth a look. For anything more I’d would look elsewhere.
 Danby, Maddin, Margesson, Rosenthal D. (1993) A randomized, double-blind, placebo-controlled trial of ketoconazole 2% shampoo versus selenium sulfide 2.5% shampoo in the treatment of moderate to severe dandruff.
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