Sulfur: The Oldest Component in Soap Chemistry

Sulfur in soap is a traditional cleansing component preferred for oily and combination skin. Sulfur is a yellow, brittle nonmetal at position 16 in the periodic table; in nature it occurs both free and within compounds. Used topically for at least 3,500 years, this mineral is part of a continuum running from the Ebers Papyrus (c. 1550 BCE) to modern cosmetic formulas. The frame of this monograph is clear: soap is a cosmetic cleanser, and the information below describes sulfur's chemical and historical profile; it carries no treatment or healing claim.

This article is not a product promotion. Its aim is to offer an independent framework on sulfur's position in the scientific literature. This is a cosmetic content monograph; it is not product or treatment advice.

What Is Sulfide?

In everyday Turkish, "sülfür" is another name for the element sulfur (S, atomic number 16); in chemical terminology, however, sulfide denotes the −2 charged ion of sulfur (S²⁻) and compounds such as iron sulfide. Sulfur is a yellow, brittle nonmetal that occurs in nature both free and in compounds; its INCI name on cosmetic labels is Sulfur, and it is used at 1–5% in traditional soap formulas.

As a yellow, naturally occurring nonmetal, this element is generally used at 1–5% in traditional cold-process soap formulas as a cleansing component for oily and combination skin types. In Turkish texts, "sülfür" and "kükürt" are used interchangeably; the bar carrying this element in the Chailea range is a natural sulfur soap.

History: an old component of cosmetic tradition

The earliest written record of sulfur's use in skin care is in the Ebers Papyrus, dated to around 1550 BCE, one of the oldest known medical texts (Doyle, 2023). According to the same review, sulfur is also mentioned in ancient Greek and Roman texts as a component of topical mixtures. Details of medieval medical traditions are not carried into this monograph, because they were not verified against a primary source.

In the modern period, elemental sulfur became a widespread topical component from the 19th century. Its popularity declined in the mid-20th century, and in recent years it has returned amid interest in "natural actives." Lin, Reimer and Carter's 1988 article "Sulfur Revisited," published in the Journal of the American Academy of Dermatology, is a comprehensive review of sulfur's historical and chemical position.

Physical and chemical properties

Elemental sulfur

Sulfur (S, atomic number 16, atomic weight 32.06) is a yellow, odorless (in pure crystal form), brittle solid. In nature it occurs both as a free element (in volcanic regions; the sulfur mines of Sicily, Italy, are historically important) and as sulfate (CaSO₄, MgSO₄) and sulfide (FeS₂, ZnS) compounds. It is allotropic, and its most stable form is the S₈ ring structure (orthorhombic sulfur).

Sulfur in cosmetic form

The main sulfur forms used in cosmetic formulas are:

• Precipitated sulfur (milk of sulfur): A fine-particle, yellowish-white powder. The most widely used form in topical products.
• Colloidal sulfur: Sulfur in suspension with a very fine particle size. Provides homogeneous dispersion.
• Sublimed sulfur (flowers of sulfur): A fine powder obtained through evaporation and condensation. It is the traditional form.

Chemical behavior of sulfur (literature)

Interaction with keratin (literature)

This mineral's interaction with keratin is a subject studied in the literature: it weakens the desmosomal bonds between corneocytes in the outermost layer of the skin (stratum corneum). This mechanism is a well-documented chemical behavior that supports the shedding of dead skin cells from the surface. The behavior is explained by polysulfides and hydrogen sulfide (H₂S), which form from the interaction of sulfur with the skin's amino acid cysteine.

In vitro microbiological studies

In in vitro studies of sulfur's metabolic transformation products (polysulfides, pentathionic acid), inhibitory activity against some bacterial and yeast species has been reported. These findings pertain to laboratory conditions and do not constitute a product efficacy claim.

Interaction with sebum

Sulfur's interaction with sebum (skin oil) is a subject investigated in the context of oily skin. The interaction of sulfur with keratin forms the chemical basis of these studies.

Place in the scientific literature

This component has long been studied in the dermatology and pharmacology literature; the review by Gupta and Nicol (2004) and Lin, Reimer and Carter's "Sulfur Revisited" (1988) are among the comprehensive assessments of this literature. The medical uses described in these studies (topical drug preparations, combinations and prescription products) belong to the context of human medicinal products and fall outside the scope of this cosmetic content monograph. The aim here is to convey sulfur's chemical behavior and its historical continuity of use; no treatment or effect claim for any disease is made.

Safety profile and warnings

General safety

Dermatology reviews report that undesired effects from topically applied sulfur are rare and mostly limited to mild reactions at the application site (Gupta and Nicol, 2004; Lin et al., 1988). According to the same reviews, about 1% of topically applied sulfur is absorbed systemically. A history of use spanning thousands of years provides context supporting the safety profile.

Possible effects and points of caution

The most frequently reported effects are skin dryness, peeling, mild irritation and transient redness; these are expected outcomes of sulfur's chemical behavior. Formulating with moisturizing components (such as glycerin, shea butter or aloe vera) mitigates these effects. At high concentrations (5%+), the likelihood of dryness and irritation increases.

Odor

Sulfur's best-known characteristic is its distinctive odor. Although pure sulfur is in fact odorless, sulfur compounds formed during its transformation on the skin can cause a "rotten egg" smell. This odor is more pronounced at high concentrations; in cosmetic formulas, masking with essential oils is applied.

Situations requiring caution

Sulfur allergy is rare but possible. Sulfonamide (antibiotic) allergy is different from elemental sulfur allergy. The review by Lin et al. (1988) reports a fatal outcome in infants following widespread application over large surfaces; therefore sulfur-containing products should not be used on babies or young children. Contact with open wounds and mucous membranes should be avoided; those with skin sensitivity or a known skin condition should consult a healthcare professional.

Sulfur in soap making

In soap, elemental sulfur is mostly included in traditional cleansing formulas aimed at oily and combination skin. The main determinants of the outcome are the correct sulfur form, the usage rate and the addition technique.

Timing and method of addition

In cold-process soap making, this mineral is added in fine powder form (precipitated or colloidal sulfur) at trace stage. To prevent clumping, dispersing it beforehand in a small amount of liquid oil (a pre-mix or slurry) is recommended. Sulfur undergoes some chemical transformations in an alkaline environment; therefore it cannot be said that all of the sulfur remains in its original form within the soap structure.

Usage rate

In soap formulas, sulfur is generally used at 1–5% of the total oil weight. In practice, this means about 5–25 grams per 500 grams of oil (1–5 teaspoons). 3% is a common and balanced starting rate. High rates (5%+) noticeably affect the soap's odor and increase the likelihood of skin dryness.

Properties sulfur adds to soap

Sulfur adds the following properties to soap:

• Color: A yellowish-greenish tint. The color becomes more pronounced as the rate increases.
• Odor: At low rates (1–3%) the odor is minimal; at high rates (5%+) a sulfur smell can be perceived. Masking with essential oils is common.
• Texture: May give a slightly grainy feel, depending on particle size (fine colloidal sulfur gives a smoother result).

Combination with juniper tar: a Turkish soap-making classic

In the Turkish soap-making tradition, using sulfur together with juniper tar to produce "juniper tar sulfur soap" is a classic and very popular formula. This combination balances sulfur's odor with the strong scent of juniper tar and brings together the characteristic properties of both components. "Sulfur soap," "juniper tar soap" and "juniper tar sulfur soap" are the names frequently used in Turkey by people looking for this traditional formula.

Frequently asked questions

What is sulfur?

Sulfur (S) is a natural element listed as element 16 in the periodic table. It is one of the older components of cosmetic tradition, with at least 3,500 years of topical use.

How does sulfur work on the skin?

Two basic chemical behaviors of sulfur are documented: its interaction with keratin (a chemical behavior linked to surface cell renewal) and the inhibitory activity reported in in vitro microbiological studies. These behaviors are explained by polysulfides and hydrogen sulfide that form as sulfur transforms on the skin (this does not constitute a cosmetic effect claim).

What does sulfur do in soap?

It is added to soap formulas at 1–5% and gives the character of a traditional "sulfur soap." Its use together with juniper tar (juniper tar sulfur soap) is one of the classic formulas of Turkish soap making.

Is sulfur soap suitable for oily skin?

This component is traditionally preferred in the context of oily and combination skin. Because it can be drying, formulas balanced with moisturizing components are preferable; using it 2–3 times a week rather than daily is a reasonable approach. Those with skin sensitivity should consult a healthcare professional.

Is sulfur safe?

According to dermatology reviews, undesired effects of topical sulfur are rare and mostly limited to the application area (Gupta and Nicol, 2004); it should not be used on babies or young children. The most frequently reported effects are skin dryness and mild irritation; products balanced with moisturizing components reduce these.

Chailea products containing this component

• Natural Juniper Tar Sulfur Soap 100 g
• Natural Sulfur Soap 100 g

References

• Gupta AK, Nicol K. The use of sulfur in dermatology. Journal of Drugs in Dermatology, 2004; 3(4):427-431. PMID: 15303787. PubMed.
• Lin AN, Reimer RJ, Carter DM. Sulfur revisited. Journal of the American Academy of Dermatology, 1988; 18(3):553-558. PMID: 2450900. DOI · PubMed.
• Doyle C. H21 Acne treatments through the ages. British Journal of Dermatology, 2023; 188(Supplement 4): ljad113.303. DOI.