Abstract
Capsule Summary
The prevalence of potential allergic contact dermatitis-causing compounds in feminine hygiene products has been inadequately explored.
After analyzing 59 pantiliners and 111 maxi pads, we identified potential allergens including wood pulp and cellulose materials, polyolefins, adhesives, pigments, fragrances, and polyethylene glycol to be prevalent in feminine hygiene products.
Our study demonstrates the need for significant steps such as additional research, standardized labeling and reporting practices, and increased consumer product awareness regarding potential contact allergens in feminine hygiene products.
BACKGROUND
Genital allergic contact dermatitis (ACD), although rare, can have a significant impact on quality of life. Common symptoms include pruritus, burning, and dyspareunia, with potential complications such as sleep disturbances and secondary infections.1,2 Diagnosing ACD can be challenging, as it often coexists with other conditions such as lichen sclerosus or lichen simplex chronicus. Furthermore, cultural taboos and feelings of embarrassment may prevent patients from seeking care, leading to underdiagnosis. 3
Pantiliners and maxi pads are widely used feminine hygiene products, but their contributions to ACD have not been adequately explored. Most pantiliners and maxi pads have the same general composition, which consists of a fluid-permeable topsheet, an absorbent core, and an impermeable backsheet (Fig. 1).4,5 The topsheet is meant to increase comfort for the wearer by keeping the surface of the pad drier. The absorbent core is designed to retain excess moisture. The backsheet is designed to prevent fluid from leaking through to the undergarment.
This figure displays the typical composition of a pantiliner or maxi pad composed of the backsheet, absorbent core, and topsheet.
Each layer of the pantiliner or maxi pad may be made from multiple different compounds with incompletely understood allergenicity. An analytic report by Desmedt et al found multiple allergenic fragrances in feminine hygiene products that were not communicated to the consumer. 6 Several case reports have also described allergic reactions to compounds found in sanitary pads, such as thyme, 7 colophony,8,9 methyldibromoglutaronitrile, 10 (meth)acrylate, 11 and perfume. 12 To the best of our knowledge, however, there exists a paucity of literature comprehensively reviewing the chemical compounds in feminine hygiene products to evaluate allergenicity. Hence, the purpose of our study was to investigate the available listed compounds in feminine hygiene products sold in the United States and explore the prevalence of previously identified allergenic compounds.
METHODS
To identify commonly available feminine hygiene products, methods similar to those described by Aschenbeck et al were employed. 13 A comprehensive search was conducted for products in physical stores in the southeastern United States and on the websites of major vendors, including Walmart, Consumer Value Store (CVS), and Whole Foods, using keywords such as “pantiliners” and “maxi pads” from August 2021 until December 2022. Duplicate products were consolidated. For items with missing online information, product packaging was examined in stores. If products were unavailable in-store or lacked ingredient lists on their packaging, manufacturers were contacted directly. Products were excluded from the analysis if ingredient lists could not be obtained through these approaches.
The compounds were grouped for analysis based on their chemical composition, structural similarities, or classification within a family of compounds, as determined by the authors’ expertise. Pigments were sorted into metallic or organic pigments based on composition, where such information was publicly available. Fragrances and botanical extracts were categorized by function rather than chemical structure. Allergenicity was initially assessed using De Groot’s Patch Testing 4th edition reference book. 14 Compounds listed in the book were deemed potentially allergenic. For compounds absent from the book, a literature search using the PubMed/MEDLINE database was conducted to identify studies on their allergic potential. Compounds were classified as nonallergenic if patch tests showed negative results or if no relevant allergenicity studies were identified.
RESULTS
Product Composition
In total, 160 Feminine Hygiene Products (FHPs) consisting of 59 pantiliners and 111 maxi pads were analyzed, and 139 unique compounds were identified. Details regarding compound grouping are provided in Supplementary Table S1. There was an average of 8.8 compounds per pantiliner and 11.0 compounds per maxi pad, though the number varied greatly by brand. There was a range of 2–22 compounds per pantiliner and 2–34 for maxi pads with a median of 8 compounds for both.
The most common compounds found in pantiliners and maxi pads were wood pulp and cellulose-derived compounds (100%), polyolefins and polyolefin copolymers (100%), adhesives and adhesive additives (88.2%), metallic pigments (80.6%), PEG and derivatives (72.3%), and unspecified pigments (61.7%). Organic pigments and azo dyes, fatty acid diester sulfates, higher alkanes, and synthetic fibers were found in over 25% of products. Antioxidants, solvents, fatty alcohol PEG ethers, fragrances, polysiloxanes, salts, and botanical extracts were also common compounds occurring in over 10% of products (Table 1).
Frequency of Compound Groups Present in Pantiliners and Maxi Pads from Highest to Lowest Total Frequency
ACD, allergic contact dermatitis.
Allergenicity
Regarding allergenicity, wood pulp and cellulose, polyolefins and polyolefin copolymers, adhesive and adhesive additives, metallic pigments, PEG, and derivatives were highly common compounds present in at least 70% of pantiliners and maxi pads. Less frequently found compounds such as fatty acid diester sulfates, higher alkanes, synthetic fibers, fatty alcohol PEG ether compounds, fragrances, polysiloxanes, botanical extracts, and fatty acid carbohydrate esters have also been demonstrated to cause contact dermatitis in prior literature (Table 1).
Unspecified surfactant was not included as a potential allergen due to its broad nature. However, several surfactants, including decyl glucoside and lauryl glucoside, have been reported as potential allergens. 15 Additional details regarding the properties of compound groups reported to cause ACD are provided in the Discussion section. Furthermore, a list of compounds found in FHPs in our review for which patch testing is available using the ACDS core series and other commercial haptens is provided in Table 2.16,17
Considerations for Compound Patch Testing for Patients Presenting with Feminine Hygiene Product-Associated Allergic Contact Dermatitis
No allergenicity reports were found for the listed ingredients in 11 feminine hygiene products (Supplementary Table S2). These included Organyc brand liners and maxi pads, whole foods organic cotton pantiliners and organic cotton pads, Walgreens organic cotton liners and heavy pads with wings (moderate), CVSHealth Live Better cotton pantiliners (light) and pure cotton pads overnight.
DISCUSSION
Our study provides a comprehensive analysis of the compounds in pantiliners and maxi pads sold in the United States and indicates that some may be significant contributors to genital ACD. A review of the current state of the literature regarding the properties, general uses, and use in FHPs of compounds found in greater than 10% of reviewed products is provided below.
Wood Pulp and Cellulose Derivatives
Wood pulp and cellulose derivatives, such as cotton and rayon, are used in the absorbent core of FHPs to retain and distribute fluid evenly, helping to keep the user dry and comfortable. 19 These compounds also provide cushioning and tensile strength for the products, potentially reducing irritation and maintaining shape. Isolated wood pulp-related ACD is unlikely to be allergenic; however, few cases have been reported for cellulose treated with other compounds such as ester plastics and sodium carboxymethyl.18-20
Polyolefins and Polyolefin Copolymers
Polyolefins and polyolefin copolymers are synthetic polymers derived from the polymerization of olefins, a class of hydrocarbons with the most common being polyethylene (PE) and polypropylene (PP). 21 They are generally light, durable, and versatile making them ideal for the topsheet and backsheet layers as a protective barrier. These plastic polymers were present in 100% of our reviewed products. The evidence for polyolefins as allergens is mixed with 2 case reports finding ACD from polyolefin esters in lubricant grease and acrylates, and 1 multicenter study not finding a clear connection.22-24
Adhesives and Adhesive Additives
Adhesives in menstrual products are typically made from a combination of synthetic polymers, resins, and additives, although some natural adhesives such as rubber and hydrogenated mineral oil are sometimes used. 19 They are typically used to attach the topsheet, absorbent core, and backsheet and are responsible for maintaining the structural integrity of the product. 88.2% of FHPs reviewed contained adhesives (although the authors postulate that almost all products contained adhesives but were not listed as an ingredient). While most FHPs simply listed “hot melt adhesive,” “adhesives,” or “hydrocarbon resin,” 5 products listed “glue” and 2 listed “pentaerythrityl rosinate” (Supplementary Table S1). Although ACD from adhesives in medical products has previously been widely reported in the literature, the allergenicity of specific compounds and additives in adhesives is not well-studied.25-27 Atwater et al in their retrospective review of cross-sectional data from the North American Contact Dermatitis group from 2001 to 2018 found 60% of nonmedical adhesive-related ACD to be caused by epoxy resin (bisphenol A). Additional relevant adhesive allergens found were methyl methacrylate, colophony, ethyl acrylate, and 2-hydroxyethyl methacrylate. 28 These ingredients were not specifically found in the FHPs reviewed and may have been listed as simple “adhesives” on the FHP ingredient list. A case report by Ito-Watanabe et al describes a case of contact dermatitis caused by a common adhesive type called hot-melt adhesive. 29 De Groot’s Patch Testing, 4th edition, also lists adhesives as an allergen (page 537). If avoidance of all adhesives is desired, other period products, such as menstrual cups, tampons, and period panties, which do not typically use adhesives, may be used.
Pigments (Metallic, Organic, and Unspecified)
In menstrual products, pigments are used to create desired appearances and increase the attractiveness of the FHPs. Various pigments from multiple sources are used with many FHPs containing more than 1 type. 19 Metallic and organic pigments, made by milling and atomizing metals such as aluminum, copper, zinc, silver, nickel, and carbon-based compounds, respectively, were 2 common categories found in our products. Many products listed pigments as “inks,” “printing inks,” and “colorants,” which were recorded as “unspecified.” Metallic, organic, and unspecified pigments were found in 80.6%, 61.7%, and 38.2% of products, respectively, making pigments a widely used compound in FHPs. Metallic pigments, common in tattoos, have been previously described as a source of American Contact Dermatitis Society (ACDs).30B31 -33 Regardless, all types of pigments and colorants have been implicated in ACD; hence, in patients with an unclear cause of ACD, clinicians must maintain a high index of suspicion regarding pigments in their feminine hygiene products being a potential reason.34B35 -38
PEG and Derivatives
PEG and its derivatives are composed primarily of repeating units of ethylene oxide. They have multiple intrinsic properties favorable for biomedical use, including hydrophilicity, nonimmunogenicity, and nonantigenicity. PEG and its derivatives are used in a broad range of cosmetic products such as surfactants, emulsifiers, and absorbents. In FHPs, they are often used to form both the surface material responsible for breathability and liquid absorbance and the backsheet material to prevent leakage. PEG and its derivatives were the 5th most common compound category (72.3%) identified in our study. Multiple single-case reports have reported contact dermatitis to various PEG compounds, although allergenicity to other PEG compounds and derivatives remains unexplored.39-41
Fatty Acid Diester Sulfates
Fatty acid diester sulfates are generally used to reduce surface tension between substances. Fatty acid diester sulfates are used widely in pharmaceuticals, personal hygiene products, and industrial agents due to their amphiphilic properties. 42 In FHPs, they are likely used to improve the fluid absorption capacity and evenly distribute moisture to prevent leakage. Although it remains unclear if these compounds come in contact with the skin, Lee et al report 1 case of ACD due to dioctyl sodium sulfosuccinate in a topical corticosteroid. 43
Higher Alkanes
Higher alkanes are mixtures of saturated hydrocarbons such as mineral oils, petrolatum, and paraffin. They are commonly used as solvents, lubricants, waxes, coatings, and in the production of fuels. Higher alkanes are also commonly utilized in cosmetic and pharmaceutical products to enhance texture and consistency. In menstrual products, higher alkanes may be used as emollients, providing lubrication and enhancing the texture, and were found in 27.1% of FHPs in our review. Among higher alkanes, mineral oil has been found to cause contact dermatitis in a single-case report, while other prior literature has reported it to be safe.44-46 Therefore, mineral oil ACD should remain on the differential diagnosis but generally be considered a diagnosis of exclusion in the absence of another obvious cause.
Synthetic Fibers
Synthetic fibers such as polyester (polyethylene terephthalate) and elastane (polyether–polyurea copolymers) are widely used fibers known for their elasticity and durability. Collectively, they were explicitly listed as an ingredient in 25.9% of FHPs. Elastane is mainly used in the panels of the menstrual pad to improve flexibility and fit, and reduce leakage, and polyesters are likely used in the topsheet or cores of the FHPs for their moisture-wicking properties. Multiple case reports have described ACD due to elastane as early as 1966.47-49 Similarly, a few instances of polyester-induced ACD have also been reported both due to industrial exposure and in personal products.22,50-52 Hence, for patients presenting with unclear sources of genital ACD, polyester should be considered as a possible culprit.
Fragrances
Fragrances can be derived from a wide variety of sources and generally provide a pleasant aroma to various personal, cleaning, and cosmetic products. Nonbotanical fragrances were found in 15.9% of products and included borneol, menthol, methyl dihydrojasmonate (Hedione), ethylene brassylate, and unspecified fragrances. Botanical extracts may be used as fragrances, but often have secondary purposes including antimicrobial and skin-soothing properties are discussed separately below. Fragrances are thought to be a common cause of ACD with Marcelis et al reporting fragrances often leaching from FHPs.53B54 -57 Yet, they are not routinely listed in the packaging. The authors specifically found menthol in 3 feminine hygiene products, which has been reported as an allergen in multiple studies in cigarettes,58,59 transcutaneous patches, 60 and medical compresses.61,62
Polysiloxanes
Polysiloxanes, commonly known as silicones, exist in various forms such as fluids and gels, and are used widely in almost all industries. They are flexible, have reduced surface tension, and can withstand high temperatures. They were found in 15.9% of FHPs reviewed and were likely used as a coating on the topsheet to reduce friction and minimize irritation. Polysiloxanes have been reported to cause ACD in various medical and personal products including toe separators, 63 continuous positive airway pressure masks, 64 cochlear implants, 65 and swimming goggles. 66 Although they are usually added to the topsheet of FHPs, the authors found no literature regarding ACD from polysiloxanes specifically in FHPs. Determining polysiloxanes as the cause of ACD may also be challenging as most patch testing centers do not routinely test for these compounds.
Botanical Extracts
Botanical extracts are plant-derived compounds used in a wide variety of personal, cosmetic, and pharmaceutical products and were found in 11.8% of FHPs in our review. In FHPs, botanical extracts such as rose, lavender, and mint are likely used as a natural fragrance alternative whereas others such as aloe might be used as a skin-soothing agent. Lavender, 67 rose oil, 68 and mint69,70 have all been reported as contact allergens in small studies and case reports. In addition, although aloe is generally considered a skin-soothing agent for skin irritation, it has also been reported as a cause of ACD. 71
Our review highlights the presence of a broad range of compounds in feminine hygiene products, often with varying names, and underscores the critical importance of increased transparency in ingredient listing for such items. These findings also emphasize the necessity for further research into the allergenicity of feminine hygiene product ingredients. Currently, only the states of California, New York, and Nevada require manufacturers to list ingredients for menstrual products, indicating inconsistent regulatory practices.72,73 During our review, many products lacked readily available materials information, either online or on their packaging. Additionally, discrepancies were noted where identical items with the same packaging displayed ingredients on 1 product but not on another. In some cases, the information provided online conflicted with what was listed on the product packaging. These inconsistencies may be harder to navigate for general consumers who seek more information but may not have the time or expertise necessary.
A lack of standard effort to list all ingredients in FHPs is likely due to how the Food and Drug Administration (FDA) classifies medical devices. The FDA classifies products into 3 categories: Class I, II, and III devices are considered low, intermediate, and high-risk products, respectively. 74 FHPs are considered Class I products and thought to be low risk, although our review identifies the need for additional research to identify consumer risks, including ACD.
Hence, we advocate for a coordinated effort by regulatory bodies and manufacturers to adopt more rigorous and standardized labeling practices by including detailed information on all ingredients used in FHPs. Increased consumer awareness and education can also play a role in mitigating the risk of ACD associated with these products. Finally, additional focus on research to investigate allergenicity of common feminine hygiene products may be warranted to help develop a more robust consumer safety profile for these products.
Patients who are found to have a contact allergy to a feminine hygiene product should discontinue using that product immediately and consult a health care professional. Dermatologists may recommend testing to help identify the specific compound the patient is allergic to. We recommend using the FHP itself for patch testing, where a piece of the product under investigation should be cut, moistened with saline solution, and applied under occlusion on the back for 48 hours. 75 Some clinicians may also rewet and reapply the home product following initial reading, leaving it in place to allow for increased compound leeching, if any, until the final read. If the clinician instead chooses to pursue commercial patch testing, Table 2 provides a list of compounds found in FHPs in our review that can be tested using the ACDS core series and other commercial haptens. We have also provided additional considerations for compounds to patch test if initial evaluations yield limited results (Table 2). If a specific allergen cannot be identified, health care professionals may consider recommending the use of one of the 11 FHPs without any ACD-causing ingredients listed in the Results section and Supplementary Table S2.
Our study has several limitations. First, not all products list ingredients consistently, hence some compounds for feminine hygiene products may have been missed. There were several products that reported only 2 compounds, which do not appear to account for the necessary adhesives and base compounds presumed to be present in all products. Second, in addition to De Groot’s Patch Testing, 4th edition, information regarding certain compounds causing ACD was derived from very small studies or single-case reports; hence, their allergenicity may not be generalizable to the entire population. Finally, since our data collection occurred in 2022, some compounds in our reviewed products have changed.
CONCLUSION
In conclusion, our findings demonstrate that pantiliners and maxi pads are potential contributors to genital ACD, with common allergens being prevalent in such products. Limited literature about the allergenicity of various compounds and the lack of standard regulatory practices further complicate efforts to identify key allergens. Therefore, significant steps such as additional research, standardized labeling and reporting practices, and increased consumer product awareness are needed to reduce the incidence of ACD from feminine hygiene products.
References
Supplementary Material
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