2% Salicylic Acid - Booster

Propanediol (1,3-propanediol) is a colourless, viscous liquid often used as a more environmentally friendly alternative to propylene glycol. It has excellent hydrating properties, making it useful in cosmetics such as creams, serums and facial toners, where it acts as a humectant and solvent. In industry, it also serves as a raw material for producing polymers and biodegradable plastics. It is well tolerated by the skin and is considered a safe, gentle ingredient. This substance is obtained by fermenting natural sources, such as corn sugar or glucose from plant materials, making it a renewable alternative to petrochemical glycols. Unlike synthetic propylene glycol, which is derived from petroleum, propanediol supports sustainability and is biodegradable, reducing the environmental footprint of cosmetic products.

Propanediol acts primarily as a humectant, hydrating the skin by binding water from its surroundings and preventing its loss through transepidermal evaporation. It improves the penetration of active ingredients into the deeper layers of the skin thanks to its ability to act as a solvent and penetration enhancer. It supports skin barrier repair by increasing hydration and elasticity without causing irritation. At concentrations of 2-10 %, it significantly improves the sensory properties of formulations, reduces the stickiness of other humectants such as glycerine, and contributes to the overall stability of emulsions.

This ingredient is ideal for dry, dehydrated, sensitive and oily skin, including acne-prone and mature skin. It is recommended for all age groups, particularly those looking for environmentally friendly, gentle ingredients without the risk of irritation. It is suitable for products for children and for sensitive areas such as the eye contour, where it replaces potentially irritating alternatives.

A study published in the Journal of Cosmetic Science (2014) demonstrated that propanediol at a concentration of 5 % improved skin hydration by 25 % after 4 weeks of application compared with a placebo, as measured by corneometry. Further research in the International Journal of Cosmetic Science (2018) reports that at a concentration of 3-7 %, it increased the penetration of niacinamide into the skin by 40 %, enhancing its hydrating and barrier-supporting effects.

This aromatic beta-hydroxy acid occurs naturally in willow bark and other plants, but cosmetic-grade salicylic acid is usually produced synthetically to ensure precise purity. It is more soluble in alcohols and glycol carriers than in water. At a low pH, it acts as a keratolytic ingredient and is one of the most extensively studied actives for oily and acne-prone skin.

Salicylic acid penetrates the oily environment within pores, loosens the bonds between dead skin cells and helps reduce the formation of comedones. It also has an anti-inflammatory effect, so it may reduce the redness of blemishes. At the right dose, it smooths skin texture, but overuse leads to dryness, stinging and disruption of the skin barrier. It should not be used alongside several strong exfoliants at once.

We recommend it for oily, combination, acne-prone and thickened skin with blackheads and blocked pores. Dry or sensitive skin can benefit from targeted, less frequent use. Extra caution and professional advice are needed for anyone with a salicylate allergy or extensively damaged skin, and for young children.

A randomised clinical study showed that 2 per cent supramolecular salicylic acid achieved similar efficacy in mild to moderate acne to a combination of 5 per cent benzoyl peroxide and 0,1 per cent adapalene, and was well tolerated (Journal of Cosmetic Dermatology, 2019). Conventional 2 per cent formulations also have long-term data supporting their ability to reduce comedones.

In Europe, it is commonly used in leave-on cosmetics within the permitted limit, often at 0,5 to 2 per cent depending on the purpose and product category. Its effectiveness depends on the pH and the proportion of free acid. SPF protection is needed during the day, and the frequency of use should be reduced if redness occurs.

When introducing targeted skincare with active ingredients, it is best to start gradually and avoid changing several products at once during the first few weeks. This makes it easier to distinguish results from irritation. Visible changes in texture or tone usually require several weeks of regular use. Daily SPF protection, gentle cleansing and a well-functioning skin barrier have a significant influence on achieving good, lasting results.