Formula Anatomy Deciphered—Feminine Hygiene Products

The term hygiene here is defined as actions or behaviors that maintain the health and well-being of the body. The word hygiene comes from the Greek term hugieinē technē, which means “the healthful art” and “having a vigorous life.” When personal care products are formulated to maintain the hygiene of the external genital area, specifically the female genitalia, they must have distinctive characteristics. These products must address the female genitalia’s complex anatomy, physiological elements and role in body metabolism and reproductive functions.

Female Anatomy

The vaginal channel, which is open to the environment through the external genital organs, is characterized by a distinctive and complex equilibrium, variable in cyclic phases during a woman’s life. This multitasking area’s uniqueness has led it to be referred to as the vaginal ecosystem.1 Its equilibrium is determined by three fundamental elements: glycogen in the vaginal epithelium tissue;2 the activity of saprophyte bacterial species;3 and the presence of lactic acid. Among the many species that colonize the human body, Lactobacillus doderlein has a positive influence for the vaginal area, as it produces lactic acid in normal, healthy conditions.3 The presence of lactic acid determines local acidic pH values, more acidic than in any other epidermal district.

The presence of glycogen (i.e., the substance that lactobacillus use as a starting raw material for the production of lactic acid) is the key biochemical element. Optimal conditions for the vaginal channel include abundant glycogen, a stable pH of 3.5–4.5 and active lactobacillus.4 This low pH value hinders the proliferation of pathogenic microorganisms such as candida, herpes and gardnerella that can enter the vagina channel from the surrounding environment. These species can induce bothersome inflammation. Modified acidity conditions due to pathology, lack of hygiene, frequent cleansing, excessively perfumed cleansers, inadequate rinse-off or aggressive cleansing may influence both the acidity equilibrium and the whole physiology of the vaginal system.5–7 (Read more about the Sensitive Skin Syndrome). The inside of the vagina is self-cleansing; therefore, the area does not normally require any special treatment. Moreover, the resident symbiotic, microbial flora protect from foreign, unwanted bacterial species.8

Feminine Hygiene Needs

Hygiene products are needed for the external part of the vagina, where the occlusion triggered by clothes, the residues of dead skin cells and the nutrient materials from traces of urine and other secretions can induce uncontrolled bacterial proliferation. Treating pH modification due to the formation of ammonia and aliphatic amines from bacterial growth, the development of bad odors and the possibility of skin inflammation requires careful cosmetic practices.

Some conditions may induce harmful changes in the vagina ecosystem. For example, immune deficiency (during menses) can promote the development of mycotic infections like Candida vulvovaginitis. Tight clothes also can be an aggravating factor, as they do not allow the moisture to wick away from the skin, supporting a warm and damp microhabitat. Moreover, some contraceptive systems and improper hygiene of the site can induce itch, promote microbial development and increase the risk of infections. (More about microbes in the human body.) The conditions of the vaginal ecosystem’s environment is complicated by the proximity of the anus, where microbial proliferation, tight clothes, hindered transpiration, sebum production and area compression from the bodyweight in seated position create maceration phenomena and additional irritation conditions.9, 10

To complicate matters, the aforementioned elements of the vaginal ecosystem evolve and present different features and needs throughout a woman’s life, from puberty to beyond menopause, and as health conditions develop.

In addition to products intended to maintain the health of the vaginal ecosystem, feminine hygiene products also include intimate hygiene products designed to increase comfort and pleasure during intercourse. Some examples of claims used for feminine hygiene products are: “with natural emollients, emollient formula; gynecologist/dermatologist/pediatrician evaluated and approved; necessary during menses; in special moments of women’s lives, hormonal changes may induce skin dryness and irritation: a mild cleanser is required; protects and helps maintaining freshness and comfort; Clinically tested: helps relief dryness and irritation discomfort; compatible with intimate skin, even irritated or intolerant to cosmetics; respects the pH of healthy mucosa, physiologic pH maintenance; provides odor reduction, fights bad odors; does not contain soap; and increases mucosa moisturization.”

The most frequently used physical forms in intimate hygiene are free flowing fluid cleansers, aerosol deodorants and lubricating/soothing gels, both aqueous and lipophilic, or emulsions, especially in anti-irritant preparations. Because of the sensitive nature of the region, transdermal diffusion testing can be helpful to determine penetration of actives. This column will divide feminine hygiene products into three main categories: personal cleansing products, personal deodorants and skin care products.11


Cleansers intended to clean the external vaginal area must be structurally different from other body cleansers. (Update on status of global bath and body care market.) The formulation strategy is different from traditional cleansers in the amount of surfactants, amount (low) of foam, ease of rinse-off, refreshing effect, antibacterial activity, pH, etc. They are considered a cosmetic, as they are applied onto the external genital area, yet they must be formulated to avoid inflammation of the skin nearby the vagina channel—as well as the anus orifice.12

Surfactants: The cleansing action of a feminine hygiene cleanser is generally based on surfactant substances, which remove the dead skin cells from the body surfaces, erase unpleasant odors and eliminate the residues of skin metabolism and any soil left from toilet use. A reduction of excess resident flora is also necessary.

The formulation strategy is to select the most delicate among the available cleansing systems. The action required by personal hygiene surfactants is a quick wetting of the skin and the residual conditioning of the intimate body parts without excessive simultaneous degreasing of the skin. Moreover, accurate rinse-off is requested, as residues of surfactant should not be left on the skin before the next cleansing/rinse. Rinse-off actions are frequently incomplete, for the anatomic complication of the area and the limited time dedicated to washing that area. Moreover, hair in the region impedes complete wash. Personal hygiene surfactants do not often produce high foam, but rather respect the skin equilibrium in the treated zone. The most used strategy to assemble the cleansing complex is blending. A high foaming surfactant such as sodium, magnesium or ammonium lauryl ether sulfate at 1–6% w/w is modified (i.e., made less aggressive for the skin) by blending with one or more mild surfactants at 1–4% w/w. Absolute concentrations depend on the foreseen dilution ratio of the final product with water. Lauryl sulfates and lauryl ether sulfates are almost never or should never be used alone due to their substantivity for the skin, excess foaming power and poor resistance to long-term hydrolysis at acidic pH.13

The most delicate surfactants for feminine cleansing are the anionic surfactants alkyl sulfosuccinates, sodium lauryl sulfoacetate and hydrolyzed proteins condensed with vegetal fatty acids, with some amphoterics like alkyl amidopropyl betaine and cocoamphoglycinates also being gentle. Among the nonionics, alkyl polyglucosides, ethoxylated glycerides or alcohols and their blends are frequently used to minimize skin degreasing. A recent alkyl glucoside line was launched by the Dow Chemical Company. The concentration of active surfactants is generally low for the above explained considerations (i.e., easy rinse-off, no residue left on the skin). Sometimes, surfactants’ concentration is just enough to reach the critical micelle concentration, as in delicate makeup removers. Recently Quillaja tree saponins have been used for their mildness, controlled foam properties and skin compatibility.14, 15 A quillaja foaming agent is offered by BioOrganic Concepts.

In respect to the skin area and mildness, lather boosters are almost never used in these systems for the same reason, as foam must be transient and decay rapidly, making rinse-off more efficient. (Read more on designing mild products.) Nevertheless, amine oxides are used in some formulations because they have skin conditioning properties at an acidic pH. An additional strategy to ensure mildness is to add some super-fatting agents like fatty acid glycerides or hydrolized proteins in the cleansing formula to reduce the aggressiveness of surfactants toward skin keratin. An interesting innovative way of eliminating soil from the skin surface is the use of a nonaggressive, non skin-dehydrating emulsifier. For example, sucrose esters, particularly sucrose laurate, do not irritate skin and do not interfere with the skin’s ability to produce and retain water. In addition, they perform some antimicrobial action toward several bacteria, including those producing bad odors, and against fungi of the Candida species without posing any harm to the resident bacterial flora.16 Recently, zinc coceth sulfate has been proposed for its antimicrobial and deodorant action, in combination with cocoyl glutamate-derived surfactants.13 Formula 1 is an example of a typical feminine cleansing formula with a surfactant system. The last ingredient is just for opacifying the product.

Acidity buffering: The second main characteristic of intimate cleansers dedicated to women is the pH value; according to many gynecologists, it should be as close as possible to 3.5–4.5, especially when the product is diluted with water. Following the blending with water, the pH of a diluted personal cleansing formula decreases to about 7. In order to prevent this phenomenon, it is a common practice to create a system buffered at an acidic pH that could maintain its value even after dilution. The ideal buffer system is partially neutralized lactic acid, as it is a well-known and safe physiological substance. Its concentration depends on the foreseen dilution ratio in the formula. It is generally buffered with an alkaline material, including the amino acid arginine. Citric acid is sometimes used, even if it is more prone to bacterial attack. Carefully buffered acids concentration can reach 5%.

Thickening: The fluidity of the intimate cleansing product must allow for proper dosage due to the area being intricately configured and allow for the use of a cleansing aid such as a sponge. Thickeners used are usually pH insensitive like hydroxyethyl cellulose, mineral clays and aluminum silicates, derived from smectic clays. These last two possess good soil-absorbing power and skin adhesion. In addition, they are efficient in removing dead cell residue and soil from the skin surface. Consequently, they work as nontraditional cleansers for the skin at 0.2–1.5%, without any foam production.

Soothing: Personal hygiene cleansing formulations may be enriched with soothing and emollient substances, possibly leaving a residual perception of comfort. Vegetal extracts and their active principles are frequently used, e.g., chamomile, mallow, sage, alpha-bisabolol. Long-lasting refreshing action is also frequently sought using mint extracts and menthol derivatives.

Obtaining skin moisturization through a cleansing formula is a difficult task, but betaine (trimethylglycine) and ectoin are good osmotic protectants that support the moisturization level of the intimate epithelium.17 Skin conditioning may be also obtained by the proper use of cationic conditioners at 0.1–3%. These must be compatible with the surfactant system.

Deodorant/perfuming: An effective cleansing performance requires a consistent olfactive message, provided by the disappearance of bad odors and the development of volatile perfume notes. For the sensitivity of the vaginal area, skin compatibility and safety of the perfumes used must be ensured. Moreover, their use percentage should be low. Nevertheless, the persistency of the notes should impart confidence that a clean body odor is ensured before and during any intimate activity. Recently, nontraditional preservative/bacteriostatic molecules such as caprylyl glycol, sodium levulinate and sodium anisate are gaining success, even though they are not included in the official Annex of allowed preservatives in the European Union.

The use of probiotics is a growing innovative trend in intimate cleansers. Recently, two German firms identified probiotic cultures useful for hygiene products. They discovered that in an anti-caries product, lactic acid-producing bacteria prevents other harmful bacteria from causing tooth decay. In skin care, the same can prevent the development of odor and support the regeneration of the skin’s protective microbial flora. Reportedly, these microorganisms can also be used in lotions or creams to help keep a healthy skin equilibrium or to improve the effectiveness of deodorants, through their ability to inhibit odor-producing bacteria on the feet and armpits. These probiotic lactic acid bacteria can be used in a live or freeze-dried form.18

Personal Hygiene Deodorants

Simple cleansing may not ensure lasting deodorant efficacy in the genital region, and a personal deodorant product may be required. Together with perfumes, these formulae contain some nonaggressive bactericides. They have a similar composition and ingredients to their underarm deodorant counterparts, but the vehicle for the antibacterial agent is a dry-feel oil such as such a short-chain synthetic ester or ethers instead of alcohol. These vehicles also deliver the perfume molecules. Some carriers are butylene glycol dicaprate-dicaprylate, octyl ether or other dry oil emollients that are actuated by aerosol systems. Alcohol is not used in these systems due to its irritation potential for this sensitive area. A mild antibacterial action is provided by bacteriostatic active ingredients, selected among the least probable to induce allergic reactions. These include polyhexamethylene biguanide or chlorhexidine chlorohydrate, which is insoluble in the vehicles.

With no need for sweat reduction in the female genital area, aluminum-based antiperspirant actives are not advisable for female hygiene products. The acidiy developed by the salt during the day could be irritating to this sensitive area. The key odor-fighting ingredient of this category of products is the perfume, which must be long-lasting and discrete at the same time (popular notes used in feminine hygiene product include iris, white flowers, talc and rose notes).

Some products in the market claim to protect the vaginal area from bad odors through the use of the perfume ingredient pentadecalactone. This is an interesting volatile ingredient with an intense musk perfume. It is present in nature in many essential oils, notably angelica roots, and in, among other fruits, pears. It is a persistent scent used in the fragrance, flavor and pharmaceutical industries.19 As some perfumes could complicate the skin irritation potential profile of the formula, adequate safety experiments should be carried out before launching the final formula. When formulating a product for an area near a mucos membrane, it is always wise to be familiar with product safety restrictions for the distribution country.

Intimate Skin Care

Intimate area skin encounters a great deal of stress from the combined actions of temperature, friction, microbes, compression and occlusion. In addition, the capability of the skin to maintain the proper grade of moisturization and mechanical properties lessens with time. An emollient and, in some cases, lubricating action is often necessary, and are progressively more necessary as age increases in order to avoid additional discomfort. For more on polymers in lubricants, read " Getting Intimate with Polymers: Personal Lubricants."

On the outer genital, for both men and women, the skin sensitivity and the thin layer skin requires efficient emollient actions. This is necessary in case of any disease leading to impaired sebum production or in any other skin imbalance. This is the field where formulator creativity has shown maximum performance.

There are two categories of moisturizing/lubricating gels: those based on glycerin gels (Formula 2), which are lubricating and water soluble; and anhydrous lipid gels (Formula 3), which are intended to exert a moisturizing and soothing action through a combination of occlusion and water organization properties. Skin lubrication without stickiness is a must in this category of products.

The most frequently used oils and fats are caprylic-capric glycerides, hydrogenated polydecenes, triethylhexanoin, shea butter and jojoba oil. They are thickened with synthetic or natural waxes, dextrin palmitate, etc.

Vegetal extracts such as thyme, sage, Eugenia caryophyllus and St. John’s wort are often used for their refreshing, soothing and mild antimicrobial actions. Either glycol or oil extracts can be used based on whether the formulation is oil-based or water/alcohol-based. Innovation The following are recent innovations in hygiene products, with more innovation to come.

Neat Feat has recently created a creama that fights against irritation in intimate zones, where the skin is subject to maximum chafing. The formula contains traditional emollients and claims to prevent skin rubbing discomfort and sweat-related skin disorders.

To provide deodorancy to the intimate area without traditional preservatives, a recent trial20 has combined the enzymatic deviator triethyl citrate with the nontraditional preservative sodium caproyl/lauroyl lactyl lactate. In vitro tests demonstrate the combination’s antibacterial efficacy, particularly against the Candida species that cause skin disorders in intimate zones, while in vivo tests show a 24-hour lasting deodorant efficacy. Triethylcitrateb is an enzymatic deviator, as it is hydrolyzed by bacterial enzymes, leading to the formation of citric acid that inhibits the further action of sweat decomposing enzymes.

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