The science behind wet wipes for infant skin
In the diapered area, the continuous exposure to excess moisture and irritants from urine and feces weakens the stratum corneum, making the skin more susceptible to irritation. The use of wet wipes for infants (baby wipes) is a common practice to clean skin after urine or a bowel movement, and this practice even extends to cleaning the hands and face, resulting in repeated daily use. Therefore, ensuring that baby wipes contain ingredients that are safe and mild on skin is important to help minimize skin irritation and discomfort. While disposable baby wipes have been shown to be effective and gentle at cleaning infant skin, even the skin of premature infants, there is growing public concern regarding their safety and tolerability. Not all products are made the same, as differences exist in manufacturing processes, ingredients, materials, safety, and quality testing. Therefore, it is important that healthcare professionals have accessible evidenced-based information on the safety and tolerability of common ingredients found in baby wipes to optimally educate their patients and families. Herein, we provide a review on best practices for ingredient selection, safety, and efficacy of baby wipes.
Skin irritation in the diapered region (commonly referred as diaper dermatitis) is one of the most common skin disorders found in infancy, with the highest incidence at 9-12 months of age.1 Overhydration and prolonged exposure to urine and feces are known to be the main contributors to skin irritation in the diapered area.2 However, an infant's diet, medications, underlying skin conditions, certain product ingredients, caretaker behavior, and practices such as infrequent diaper changes or ineffective cleaning can also influence the occurrence of diaper dermatitis. It has been reported that the diapering process can be a stressful event for an infant.3 The presence of skin irritation can exacerbate this response, leading to increased pain and discomfort. Ensuring the diapered area is kept dry and clean and that products used do not adversely impact the skin can help minimize the occurrence of dermatitis in the diapered region and, in turn, provide comfort to the infant.
Herein, we provide a review on best practices for ingredients selection, safety, and efficacy of runhe baby soft wet wipes to help make more informed decisions when selecting products for infant diapered skin care.
A disposable baby wipe consists of three main components—the basesheet (the cloth that makes the wipe), the formulation (the ingredients in the solution that make the wipe wet and help with cleaning), and package, as shown in Figure 1. The packaging (not discussed here) and the basesheet are the most physically obvious components of a wipe. There are three types of basesheets with differences in composition which translates into differences in thickness, absorbency, and softness to touch. These differences can impact cleaning performance but the materials themselves are quite common—wood pulp, polypropylene, polyester, or combinations thereof.
Over the last two decades, significant advances have been made to baby wipes. More recently, efforts have been centered on the removal of ingredients with irritation or skin-sensitizing potential such as methylisothiazolinone (MI) and phenoxyethanol.4 In fact, five clinical studies have demonstrated that the use of modern baby wipes is superior to using water and cloth to clean diapered skin (see Table 1). In 2016, a recommendation was made by the European Roundtable Meeting on Best Practice Healthy Infant Skin Care stating that a wet wipe for infant skin should contain pH buffers to maintain the slightly acidic pH of the skin, should be free of potential irritants, and should contain well-tolerated preservatives
Formulating a hypoallergenic, safe, gentle, and effective baby wipe can be challenging as the wipe must meet regulatory, safety, and performance measures while remaining aesthetically pleasing. It is preferred that baby wipes are formulated with a very large percentage of water. However, water alone is not enough to effectively remove water-insoluble residues from feces and prevent the growth of microorganisms or maintain a healthy skin pH. Thus, it is important that baby wipes also contain an extremely mild surfactant (detergent or cleanser) to lower surface tension for better cleaning, a preservation system to ensure product freshness before and during use, a pH adjusting (buffering) system to maintain a solution pH similar to infant skin, and, optionally, skin-benefiting ingredients that reduce frictional damage, replenish the skin lipids, etc A common misconception about baby wipes is that they contain drying alcohols such as ethanol and isopropanol. While ethanol and isopropanol can be found in some sanitizing wipes, these ingredients have not been used in branded baby wipes.
The water used in baby wipes should range from highly purified to reverse osmosis quality. The treatment process removes most of the salt content (CaCO3 and MgCO3, contributing to overall hardness) and other residual minerals that can serve as nutrients for microorganisms. Most water systems also employ ozone and ultraviolet light processing to sterilize the water before use. In addition, extensive filtration removes total dissolved solids and microbes. These intentional processes produce water that is of a higher quality than standard drinking water and some types of distilled water.
Surfactants are the molecules within the formulation that provide cleaning action. Surfactants contain hydrophilic moieties attached to hydrophobic end chains. It is the hydrophobic end chains that bind to oily residue on the skin surface and help remove it. For baby wipes, it is important to use a surfactant that can adequately remove the oily molecules within feces without removing skin lipids, which can lead to skin barrier damage with repeated or prolonged use. For runhe new arrival baby wipes, the surfactant fraction would not be expected to exceed 1% by weight of the formula and, in most cases, would be below 0.3% by weight.6 This is in stark contrast to bottled baby products (body wash, shampoo, hand soap) where the surfactant concentration is typically between 5% and 20% by weight as dilution is expected upon use followed by rinsing.6
Surfactants are typically classified as anionic (negatively charged), cationic (positively charged), and non-ionic (no net charge). Generally, non-ionic surfactants are the mildest on skin; however, there are examples of suitable surfactants in all classifications. Table 2 contains a list of typical baby wipe surfactants along with maximum use concentrations and references to full reviews on their safety profile as concluded by the Cosmetic Ingredient Review (CIR), an independent expert panel consisting of dermatologists, toxicologists, academic researchers in medicinal and pharmaceutical sciences, industrial scientists, and representatives from the FDA and consumer groups.
As baby wipes contain a large amount of water, this can allow microorganism growth. To prevent contamination, various manufacturing and testing practices are followed by major suppliers. The use of preservatives ensures the product is not contaminated before the consumer begins using it, and that it maintains a reasonable shelf life for use. Ensuring a consistent product, free of pathogenic microorganisms, should be of the highest concern, especially when cleaning infants with compromised skin.
In the personal care industry, the default listing of preservative chemicals is maintained by the European Union (EU) and is known as Annex V.7 Ingredients on this list are recognized for their antimicrobial action and listed with acceptable and safe usage concentrations. A subset of these chemicals applicable to baby wipes is shown in Table 3. Notably, many of the chemicals in Annex V are not allowed for use in children's products due to regulation at the state or country level. The US FDA does not maintain a list of approved preservatives but does have the authority to limit the use of ingredients in certain product classifications. After considering safety, allergenicity and irritation potential, the choice of preservative in a formulation depends on water solubility, effective concentration, pH compatibility, odor, and consumer expectation. A good example of regulatory and industrial response has been the removal of formaldehyde donating preservatives and MI from wipes and other leave-on products following many reports of contact dermatitis and sensitization in the diapered area and in other common areas of baby wipes use such as hands and face. Currently, it is rare to find this ingredient in mainstream baby soft wet wipes.
A critical part of ensuring baby wipes are safe and effective to clean infant skin is following specific microbiological quality standards prior to product distribution. As is the case with most non-sterile formulated personal care products, baby wipes require specific analyses to ensure they (1) do not contain harmful or high levels of microbes following manufacturing and (2) can control the growth of microbes introduced during use. Non-profit scientific organizations, such as the United States Pharmacopeia (USP) and the European Pharmacopeia (EP), have published guidelines on the preferred approaches for completing these analyses.
Prior to releasing baby wipes for sale to consumers, an evaluation of the final product should be completed for the presence and level of microbes within the product. For example, the USP recommends that methods used in the release of non-sterile products have data available that demonstrates the ability for methods to successfully recover and quantify Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, Candida albicans, and Aspergillus brasiliensis.21
Any products that have a water activity level of >0.90 are susceptible to the growth of microbes in the product as this is the minimum level of water required for bacteria and fungi to grow.22-24 As such, products at or exceeding this level of water, such as wipes, should include a preservative to prevent the growth of microbes that may be introduced post-manufacturing. A likely route of post-manufacturing product contamination is while dispensing the product during use,25 a reason why packaging is a key component. In this scenario, transient or normal flora from a wipes’ user can transfer from the hands onto the stack of wipes in the product package. To assure a newborn baby wipes product is effectively preserved and able to overcome this type of contamination, a confirmatory lab test must be utilized to ensure microbial growth will not occur during normal product use. Specifically, the test should involve adding a defined number of diverse organisms (at a minimum those recommended by USP/EP but others may be added) to a defined quantity of product and then monitoring the survival and/or growth of the added organisms over time.26 This test is commonly utilized on product that has been freshly made and on product aged under ambient or accelerated (high temperature, high relative humidity) conditions. While there is no universally applied approach in how this test is conducted for wipes, many manufacturers utilize USP and/or EP guidance as the basis for establishing their method and acceptance criteria.
The performance of the preservative system is one of the most important factors that go into determining the expiration date on the package. Baby wipes that do not have a proper preservative system should have a much shorter expiration date (or period after opening) as the product does not have a means to prevent microbial growth post-manufacturing. This is especially critical when the dispensing of the wipes requires significant contact by human hands, that is, transfer of normal flora into the package. Wipes should not be used outside of the printed expiration dating on the package and should be stored as directed by the labeling on the package.