Lactoperoxidase is an enzyme found naturally in milk, saliva, and other body secretions, and it plays an important role in the innate immune defense of mucosal surfaces, including those in the oral cavity and respiratory tract. Scientific studies have shown that lactoperoxidase can catalyze the oxidation of thiocyanate ions in the presence of hydrogen peroxide, producing hypothiocyanite, a compound with antimicrobial properties. This system, known as the lactoperoxidase system, inhibits the growth of various bacteria, viruses, and fungi on mucosal surfaces, thereby contributing to the maintenance and protection of mucus membranes.

Several in vitro and in vivo studies have demonstrated that supplementation or activation of the lactoperoxidase system can reduce microbial colonization and may be beneficial in managing oral health issues such as dental caries, gingivitis, and oral infections. It is also used in some commercial oral care products for this reason. While much of the evidence comes from studies on oral health, the enzyme’s presence and function in other mucosal secretions suggest a broader role in mucosal immunity. However, clinical evidence specific to other mucosal surfaces (e.g., nasal or gastrointestinal) is less robust, which is why a rating of 4 is given rather than 5.

In summary, there is substantial scientific basis for the use of lactoperoxidase to support the health of mucus membranes, particularly in the context of oral and possibly respiratory mucosa, due to its well-characterized antimicrobial activity.