I Provenzali Saponetta Purificante Allo Zolfo

You'll also recognize water as that liquid we all need to stay alive. If you see this, drink a glass of water. Remember to stay hydrated!

When sulfur touches skin, it reacts with an amino acid in skin cells (called cysteine) to create cystine and hydrogen sulfide.

That hydrogen sulfide helps loosen dead skin cells to exfoliate. And here's a geeky detail: the smaller the Sulfur particles, the more they interact with skin and the better they work.

Sulfur also has antifungal and antibacterial activity, which is why you'll see it in both acne treatments and dandruff shampoos.

In the US, acne products can use 3-10% sulfur while dandruff products use 2-5%. It's also often paired with Sodium Sulfacetamide, and using that combo twice daily for 12 weeks reduced inflammatory acne spots by about 80%.

The most common complains are the smell and dryness. Otherwise, side effects are uncommon.

If you have a "sulfa" allergy, that's an allergy to sulfonamide drugs and this doesn't mean you'll react to elemental sulfur.

A 1972 study suggested sulfur might clog pores. Elemental sulfur caused some clogged pores on rabbit ears and human backs (though the researchers noted the effect was mild).

A 1978 follow-up tested this on 52 people. After six weeks of patches with 5% Sulfur, skin biopsies showed no link between Sulfur and clogged pores. The surprise? The base the Sulfur was mixed into was what caused clogged pores. Later reviewers also noted that other studies couldn't repeat the 1972 results.

So why does Sulfur have a comedogenic rating of 3?

That number comes from a 1989 rabbit ear study by dermatologist James Fulton, which gave a 3 to water-soluble sulfur specifically. Even so, a 3 isn't a big red flag. Fulton's own scale treats 2 to 3 as borderline.

Human testing has also proved that any finished product with a comedogenic ingredient won't automatically make you break out; it really comes down to concentration, formula, and your skin.

Your skin makes glycerin on its own (mostly from sebaceous oil breakdown) and shuttles it to your outermost layer of skin, or your epidermis, via aquaporin-3.

Aquaporin-3 is a transporter that is essential for normal skin hydration, elasticity, and repair. Interestingly, mice lacking in AQP3 have dry and less elastic skin that can be fully corrected with glycerin.

This ingredient is non-irritating, plays well with almost every ingredient, and works across all skin types. Typical use is anywhere between 3-10% but can go up to 79% in some leave-on products.

Just know very high concentrations (>40%) can feel tacky in low humidity.

Glycerin is the name for this ingredient in American English. British English uses Glycerol/Glycerine.

Squalene is also naturally present in olive oil and exhibits moisturizing and antioxidant properties.

The polyphenols in olive oil also show anti-aging promise; one clinical study found a measurable improvement in skin appearance after 30 days of topical serum use.

Just be aware that applying olive oil directly to skin can weaken the barrier and cause redness. One study with volunteers found even people without sensitive skin experienced a significant reduction in stratum corneum integrity and induced mild erythema.

It's best to use this ingredient as part of a carefully crafted formula (instead of putting it on skin directly from the bottle).

Because it has a 0-2 on the comedogenic scale, it is low risk for acne-prone skin. Just remember the overall formulation of a product matters more than a few ingredients with comedogenic ratings.

This ingredient may not be fungal acne safe because of the oleic and palmitic acid content. These fall within the C11-24 fatty acid range that the Malassezia yeast can metabolize to grow.

Overall, olive oil is a well-studied and nourishing skincare ingredient.

As an emollient, it softens and hydrates skin by forming a thin barrier that locks in moisture.

Clinical studies have found it to be non-irritating and non-sensitizing. The CIR Expert Panel has evaluated the available safety data and concluded it is safe for topical use.

Because of the oleic acid content, this ingredient may not be fungal acne safe.

This ingredient does have a comedogenic rating of 3, but this doesn't mean a formula with this ingredient will clog pores.

Human testing has proved that any finished product with a comedogenic ingredient won't automatically make you break out; it really comes down to concentration, formula, and your skin.

It plays well with most ingredients and is typically used at 0.1-1%. However, concentrations up to 50% have been reported in moisturizers.

However, this exfoliating effect only happens at high concentrations (20%) which can be hard to find in cosmetic products.

Due to this, citric acid is usually included in small amounts as a pH adjuster. This helps keep products slightly more acidic and compatible with skin's natural pH.

In skincare formulas, citric acid can:

While it can provide some skin benefits, research shows lactic acid and glycolic acid are generally more effective and less irritating exfoliants.

Most citric acid used in skincare today is made by fermenting sugars (usually from molasses). This synthetic version is identical to the natural citrus form but easier to stabilize and use in formulations.

Rosacea skin has a lower threshold for acids generally, with 62.5% of rosacea subjects in one study reacting to lactic acid in a sting test. This is why we mark citric acid as a potential rosacea trigger.

However, this ingredient shows up as a pH adjuster or chelator at roughly 0.1-1% in many products. These low levels are unlikely to be an issue for rosacea skin and becomes a potential trigger at exfoliating concentrations (20%). Because everybody's skin is unique, we recommend a patch test if you are unsure.

You might see people debate whether Sodium Chloride is comedogenic, but there actually haven't been any comedogenic tests done on it. Either way, the overall formulation of a product matters a lot more than any single ingredient.

You might see this ingredient used in scrubs as a primary exfoliating ingredient.

The EU requires it to be named on the label above 0.001% in leave-on and 0.01% in rinse-off products.

Fresh linalool is a weak sensitizer but air exposure turns some of it into hydroperoxides, which are strong sensitizers. Those oxidation products are the actual allergy concern.

Patch-test clinics see positive reactions to linalool hydroperoxides in about 4% to 12% of dermatitis patients depending on country and test concentration.

Resassuringly, one analytical study found hydroperoxide levels in real fragranced products to be orders of magnitude below what induced sensitization in animal studies with no evidence of oxidation building up during normal storage.

The practical takeaway is that linalool is fine for most people but worth avoiding if you have a confirmed fragrance contact allergy or a badly compromised barrier.

Products stored a long time after opening are also the high-risk scenario since that is when oxidation happens.

The scent of linalool is described as floral, spicy tropical, and citrus-like.