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Sulfur as a treatment for scabies?

Known since antiquity, scabies is an "ancient" disease for humans, caused by a mite that lives its entire life cycle in the skin of its host. Identified as first-line treatments, several local anti-scabies therapies have been used and have proven effective topically, including sulfur. Let's learn more about the effectiveness of this non-metallic natural mineral on this highly contagious parasitic disease.

Summary
Published September 5, 2023, updated on June 17, 2024, by Stéphanie, Doctorate in Life and Health Sciences — 8 min read

Scabies: What should you know?

Often mistaken for eczema or impetigo, human scabies is a parasitic infestation caused by mites about 0.4 millimeters long, Sarcoptes scabiei variant hominis, which have the ability to penetrate the host's epidermis to reproduce there. The average number of mites hosted by the host is usually less than 10, except in the case of "crusted scabies", where the host can harbor more than a million mites.

It is the adult female that plays a major role in the pathogenesis of scabies, while the adult male, nymphs, larvae, and eggs have a lesser effect in causing the disease. After fertilization, the female settles just below the skin surface, where she begins to burrow a tunnel in the horny layer at a rate of 1 to 2 millimeters per day, laying between 2 to 3 eggs per day. After 3 to 5 days, the eggs hatch and transform into adult mites within two weeks.

After 4 to 6 weeks, the infected patient develops an allergic reaction due to the presence of mite proteins and feces, which leads to itching of varying intensity and nocturnal resurgence. Other clinical signs may also occur, but inconsistently, such as a skin rash (pruritic papules and nodules) or scabies burrows sometimes ending in a slight elevation, corresponding to the path taken by the mite. These lesions are generally located on the spaces between the fingers, the front of the wrist and elbow, the armpits, the lower part of the buttocks, the inner thighs or the male genital organs. The face is usually spared.

Contagious, scabies is transmitted in the vast majority of cases through close and prolonged skin contact, and this risk of transmission increases proportionally with the quantity of parasites present (the highest risk being associated with contact with individuals suffering from crusted or profuse scabies). On the other hand, indirect transmission through infested objects (clothing, bed linens, etc.) is a less common occurrence in the case of classic scabies, but can be significant for individuals suffering from crusted or profuse scabies.

Given that there is an asymptomatic period of infestation, transmission can occur before the initially infested person develops symptoms. Present worldwide, scabies is more common in warm and tropical countries, as well as in areas with high population density. It is estimated that there are approximately 300 million cases of scabies each year worldwide.

Note : Outside of its human host, the mite responsible for scabies has a short lifespan, on the order of 1 to 2 days. Similarly, at a temperature below 20°C, the adult female loses her mobility and dies quickly (within 12 to 24 hours); above 55°C, the mite is killed in a matter of minutes.

The direct effects of scratching can lead to theinoculation of bacteria into the skin, which results in the development of impetigo. Impetigo can further complicate into a deeper skin infection, such as abscesses or a serious invasive disease, including septicemia. Moreover, in tropical regions, skin infection associated with scabies is a common risk factor for kidney disease and potentially rheumatic heart disease.

Similarly, individuals with weakened immune systems (immunocompromised), including those living with HIV, may develop a condition known as crusted scabies (Norwegian). This severe infection can harbor thousands, or even millions of mites, and cause areas of dryness and scaliness (hyperkeratotic lesions) and widespread redness over most of the skin surface (erythroderma). Moreover, crusted scabies can spread very easily and thus lead to secondary infections.

Treating scabies using sulfur?

A variety of topical products (acaricides) are available to treat scabies by destroying the mites and their eggs, such as the daily application of a sulfur cream/ointment with typical concentrations ranging from 5 to 10% for 3 to 5 consecutive days/nights, followed by a four-day break to allow the eggs to hatch before repeating the procedure for an additional 2 to 3 days for a high cure rate.

Numerous clinical studies have demonstrated the effectiveness of applying a sulfur ointment to eradicate scabies, often in a single dose. According to a study conducted on 420 patients with scabies, administering a single oral dose of ivermectin would be equivalent to a single application of a sulfur ointment after two weeks. A recent study also sought to investigate and compare the effectiveness of 5% permethrin cream and 10% sulfur ointment in the treatment of scabies on 218 patients. The researchers found that the mites show reduced sensitivity to 5% permethrin compared to the sulfur ointment.

The sulfur is the oldest known treatment for scabies, recognized throughout history. In the early 19th century, sulfur fumigation was used to treat those afflicted with scabies. This method, conceived by Galès, involved placing patients in boxes and permeating them with sulfurous fumes. Several centuries ago, physicians also used it by painting the entire body of the infected patient with sulfur powder mixed with oil to treat scabies, as well as pediculosis and acne.

By what mechanisms?

Sulfur is believed to be toxic to the scabies mite (Sarcoptes scabiei). It is thought to work by inhibiting the growth of the parasite. According to studies, its parasiticidal activity may result from its conversion into pentathionic acid by skin cells (keratinocytes) and skin bacteria when applied to the skin. Additionally, the keratolytic action of sulfur may aid in the removal of parasites from the stratum corneum.

However, the high content of sulfur can be associated with a high incidence of side effects, particularly if it is used over a prolonged period. It can cause intense itching and skin dryness, and in the most severe cases, it can even lead to ichthyosis (a severe form of skin dryness that involves excessive skin peeling).

Sulfur is safe for pregnant and breastfeeding women. However, to date, the safety of this treatment has not yet been tested on infants and is not recommended for children under six years old.

Sources

  • STOWERS J. H. Treatment of scabies by sulphur fumigation. Proceedings of the Royal Society of Medicine (1917).

  • NOLAN R. A. Sulfur soap paste in the treatment of scabies. Archives of Dermatology and Syphilology (1937).

  • CARTER D. M. & al. Sulfur revisited. Journal of the American Academy of Dermatology (1988).

  • ACOSTA M. & al. Efficacy, safety and acceptability of precipitated sulphur petrolatum for topical treatment of scabies at the city of Coro, Falcon State, Venezuela. Revista de Investigación Clínica (2004).

  • AL-HASSANY H. M. & al. Treatment of scabies using 8% and 10% topical sulfur ointment in different regimens of application. Journal of Drugs in Dermatology (2012).

  • REZAEE E. & al. Comparative trial of oral ivermectin versus sulfur 8% ointment for the treatment of scabies. Journal of Cutaneous Medicine and Surgery (2013).

  • GOLDUST M. & al. The efficacy of oral ivermectin vs. sulfur 10% ointment for the treatment of scabies. Annals of Parasitology (2015).

  • OWCARZ M. & al. Comparative efficacy of topical Pertmehrin, Crotamiton and sulfur ointment in treatment of scabies. Journal of Arthropod-Borne Diseases (2017).

  • AKTAS H. & al. Comparison of sulfur ointment and permethrin treatments in scabies. Dermatologic Therapy (2022).

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