Sulfur

Sulfur has been put on skin for longer than dermatology has existed as a discipline. It survives in the regulations because it works, and it is the neatest illustration on this site of how the American drug monographs are actually organised.

The same element, two legal strengths

Sulfur appears in two separate monographs with two different ranges.

For acne, the regulation permits “sulfur, 3 to 10 percent”, and “sulfur, 3 to 8 percent, when combined with resorcinol or resorcinol monoacetate”.

For dandruff, it permits “sulfur, 2 to 5 percent”.

Nothing about the element changes between those two lines. What changes is what the product claims to treat, and the monographs are indexed by purpose rather than by substance.

That sounds like a technicality and it has a practical consequence: a product’s legal ceiling depends on what its box says it is for. An anti-dandruff product cannot carry acne-strength sulfur while calling itself an anti-dandruff product, even though the same shelf sells both.

Salicylic acid does exactly the same thing, at 0.5 to 2 percent for acne and 1.8 to 3 percent for dandruff. Two ingredients, one pattern, and the full table is in the list of ingredients that are legally drugs.

What it does

Sulfur is keratolytic, meaning it helps shed the outer layer of skin, and it is antimicrobial against some of the organisms involved in acne and in seborrheic dermatitis.

It is slower and gentler than Benzoyl peroxide, which is the main reason it persists as an option: it suits skin that benzoyl peroxide strips. It is also less well studied than the more modern actives, which is the honest counterweight.

The smell is the reason most people stop. Formulation has improved it and not solved it.

Reading the label for it

Sulfur products carry a drug facts panel, because they are drugs. The panel names the active and its strength, so this is one of the few places in a bathroom where you can compare two products on a number.

Resorcinol appears alongside it in some older formulations and is permitted only in that combination, at 2 percent. Seeing resorcinol on its own for acne is not a monograph configuration.

On the scalp

For seborrheic dermatitis it sits alongside Pyrithione zinc, selenium sulfide and Coal tar in the same monograph.

The dermatology guidance for textured hair applies to sulfur as it does to the rest of that group: apply it to the scalp rather than the lengths, and do not leave it on longer than directed, because prolonged contact time is not needed for a medicated shampoo to work. That is set out on the curly and coily hair page.