Lactoperoxidase

Imagine an enzyme that acts as a frontline defender in your skincare, harnessing the power of nature's own antimicrobial system. That is Lactoperoxidase, a naturally occurring enzyme originally found in milk, saliva, and tears. Chemically, it belongs to the peroxidase family, which means it catalyzes the oxidation of thiocyanate ions (also present in your body) to produce hypothiocyanite, a gentle but potent antimicrobial agent. This system is part of the innate immune system in mammals, designed to protect mucosal surfaces and secretions from harmful microbes without causing inflammation. In cosmetics, lactoperoxidase is typically sourced from bovine milk or produced via biotechnology, ensuring purity and stability for formulation.

In skincare products, lactoperoxidase works as part of what is often called the "lactoperoxidase system," which also includes glucose oxidase, glucose, and potassium thiocyanate. When applied to the skin, glucose oxidase converts glucose into hydrogen peroxide, which then activates lactoperoxidase to convert thiocyanate into hypothiocyanite. This cascade creates a sustained, low-level antimicrobial effect that targets bacteria, fungi, and even some viruses, without disrupting the skin's beneficial microbiome. Formulators typically use it at concentrations between 0.01% and 0.1%, as it is highly effective in tiny amounts. Its primary INCI function is listed as stabilising because it helps preserve the product's integrity by preventing microbial growth naturally, reducing the need for harsh synthetic preservatives.

The main benefits of lactoperoxidase in skincare are its ability to act as a gentle, broad-spectrum antimicrobial agent that supports the skin's natural defenses. Unlike many traditional preservatives or antibacterial ingredients (like alcohol or benzalkonium chloride), it does not indiscriminately kill all microbes—it selectively targets pathogens while leaving beneficial bacteria largely unharmed. This makes it ideal for maintaining a healthy skin microbiome, which is crucial for conditions like acne, eczema, or sensitive skin. Evidence for its efficacy is moderate; it has been well-studied in oral care and wound healing, but research in topical cosmetics is growing. It also has mild antioxidant properties, as it can neutralize some hydrogen peroxide before it causes oxidative stress, adding a layer of protection for the skin.

This ingredient is especially well-suited for sensitive, reactive, or acne-prone skin types because it is non-irritating and works synergistically with the skin's own biochemistry. It pairs beautifully with other gentle ingredients like niacinamide, zinc, and prebiotics, as all support a balanced microbiome. However, it may not be compatible with very low pH formulations (below pH 4.5) or high concentrations of strong acids, as this can denature the enzyme. Also, because it relies on a cascade of co-factors (thiocyanate, glucose, and glucose oxidase), the full system must be present in the product for it to work—if any component is missing, the antimicrobial effect is diminished. There are no known toxicity concerns at typical cosmetic levels, but those with severe milk allergies should check the source, as bovine-derived lactoperoxidase could theoretically trigger a reaction, though this is extremely rare.

When shopping for products, you will often see lactoperoxidase listed alongside glucose oxidase and potassium thiocyanate on the ingredient label, sometimes marketed as a "natural preservative system" or "bio-ferment complex." It is commonly found in leave-on products like serums, moisturizers, and toners, as well as in some cleansers and masks. One interesting fact: the lactoperoxidase system is the same mechanism that helps protect breastfed infants from infections, as it is present in human milk. In cosmetics, it adds a touch of biological elegance—instead of relying on harsh chemicals, it mimics your body's own antimicrobial strategy. Because it is an enzyme, products containing it should be stored away from extreme heat or direct sunlight to maintain its activity. If you see it in a formula, you can feel confident that the brand is prioritizing microbiome-friendly preservation without compromising safety.