Rumor: Women are advised not to use cool sanitary napkins such as additive, herbal, fragrant and other hygiene products! Cool sanitary napkins feel cool because the sanitary napkins in the surface material added mint agent, mint agent in the process of use will be slowly released, thus destroying the weak acid environment of the genitals, the destruction of the weak acid environment will make the genitals own resistance to decline! The use will make the menstrual flow less and less. Editor’s note: Since the packaging of cool sanitary napkins on the market is not marked with their added ingredients and added amounts, we have no way to tell exactly whether it will have beneficial or harmful effects on the human body. This article only briefly analyzes whether the addition of mint-like substances to cool sanitary napkins is harmful to women’s health. Truth: The use of cool sanitary napkins does not destroy the weak acidic environment in the vagina and does not lead to low menstrual flow. As long as they are hygienically qualified sanitary napkins, the type used is just a matter of personal habit. However, it should be noted that women with sensitive skin and allergies should use sanitary napkins with added fragrances and medicated ingredients with caution to avoid skin irritation and allergic reactions. The cool sensation of sanitary napkins is usually the sensation of the skin or mucous membranes to the temperature, however, not all the “cool” feeling is due to the change of temperature. Mint contains a substance called menthol, and this substance and some of its derivatives can stimulate the cold receptor TRPM8 receptors (a special protein) in the skin and mouth, allowing the body to produce the sensation of “cold” without actually changing the temperature. TRPM8 receptors are found in sensory neurons and were once called “cold and menthol receptor 1” (CMR1). As the name suggests, chemicals such as menthol activate this receptor like cold itself, producing the sensation of “cold”. It is 200 times stronger than menthol [2]. In addition, linalool, citronellol, hydroxycitronellal, menthamide (WS-3, WS-23), menthol glycerol ketone, and menthyl lactate are also agonists of the TRPM8 receptor and produce a chill sensation [3]. (See Shell Q&A: Why does mint make my mouth cold when I eat it? Is it any different than eating ice cubes and getting cold in the mouth? Can menthol disrupt the weak acidic environment of the vagina? We know that the vagina is not a sterile environment, but the balance of its microecological environment provides a defense against the invasion of external microorganisms, called vaginal self-purification. Estrogen, Lactobacillus vaginalis and the vagina’s weak acidic environment are three important components of the vagina’s ability to cleanse itself. （When one or more of these three components are broken, the vagina’s defenses are reduced and it becomes vulnerable to exogenous pathogens, leading to vaginitis. Studies of menthol have shown that menthol itself has some antibacterial properties, which is the source of the rumor that it “destroys the weak acid environment of the genitalia”. If menthol inhibits the reproduction of Lactobacillus in the vagina, it could theoretically lead to a disruption of the weak acidic environment of the vagina, making the user vulnerable to vaginitis. In practice, however, it should be noted that the minimum inhibitory concentration (MIC) of menthol for most bacteria is about 0.04-0.2 mg/mL [4], which translates to about 40-200 ppm (1 ppm is one part per million). In contrast, the threshold of cool sensation of menthol is around 0.8-3 ppm [5], and the concentration required to produce a cool sensation is much less than the minimum antibacterial concentration of menthol. The concentration of menthol used topically may not reach the minimum antibacterial concentration if it is used only for the purpose of producing a cool sensation on the skin or mucous membranes. Also, if you are using a sanitary napkin with menthol, which is placed near the vaginal opening and not a tampon, the amount of menthol that can actually enter the vagina is very small and does not reach its minimum antibacterial concentration. Therefore, it is probably unnecessary to worry that the tiny amount of menthol added to the sanitary napkin will have an effect on the normal flora in the vagina. Can menthol cause less menstrual flow? There are many claims on the internet that menthol can enter the uterus and cause uterine chills, leading to abnormal menstruation. Is this true? The concept of “coldness in the uterus” in modern medicine corresponds approximately to the symptoms of dysmenorrhea and menorrhagia. The cause of dysmenorrhea is mainly due to excessive secretion of prostaglandins during menstruation, which causes excessive contraction of the smooth muscle of the uterus and vascular contracture (see Girls’ Time: Sister’s pain is not menstruation, but loneliness). Although cold can also cause contraction of the uterine smooth muscle and blood vessels and may aggravate dysmenorrhea, but it is not the main cause of dysmenorrhea. The reason for this is that menstruation is usually related to endocrine disorders and endometrial thinning caused by uterine operations such as curettage and abortion. For one thing, menthol does not have the pharmacological effect of sex hormones and does not affect endocrine secretion, so it does not affect menstruation. Secondly, the uterus and vagina are two relatively isolated environments, and the cervical opening is only slightly opened during menstruation in order to discharge the menstruation produced in the uterine cavity. Don’t believe in the so-called efficacy of herbal sanitary napkins Although these cool sanitary napkins are unlikely to be harmful to pubic health, these menstrual products with other ingredients do require some attention. Some so-called herbal sanitary napkins advertise certain health and healing benefits for women, which should not be taken lightly. Because on the one hand there is no reliable evidence that these advertised effects are actually effective, and on the other hand, because of the dense structure of the skin and the limited absorption of drugs, even drugs that have proven effective in other areas do not mean that they are equally effective when used on sanitary napkins (a particularly rugged way of delivering drugs). In addition, for women with sensitive skin and allergies, it is important to be aware of possible skin irritation and allergic reactions to the use of such sanitary napkins with added fragrances and medications. In short, the “efficacy” of cooling sanitary napkins is simply that the cooling sensation they produce is a comfortable experience for some users, and it is up to the consumer to decide how to choose. Conclusion: Rumor mongering. The use of cool sanitary napkins will not destroy the weak acidic environment in the vagina, and will not make menstrual flow less, and the cool feeling it brings is a comfortable experience for some users. Author’s words: The lesson for manufacturers is that they should be careful about adding drugs and additives to personal care products that come into direct contact with the skin. For controversial additives, the chemical composition and the amount added, as well as its possible effects and side effects should be indicated. This not only respects the consumer’s right to know and makes them feel more at ease when using them, but also avoids the negative impact of rumors on the product through facts.