Researchers at the University of Jiroft in Kerman Province, Iran, set out to test whether aloe vera gel, used as an edible coating and enriched with fennel or lime peel essential oils, could extend the shelf life and microbial safety of table eggs stored under refrigeration. The team, led by Zahra Ranjbarinasab and Fatemeh Shahdadi, noted that although aloe vera gel and various essential oils have each been explored for egg preservation before, no previous study had investigated this particular combination for maintaining both the physicochemical quality and microbial stability of refrigerated eggs. Their findings point toward a natural, additive-free approach that could reduce food waste and economic losses in one of the world’s most consumed animal products.

The experimental design was straightforward but rigorous. The researchers obtained 300 fresh white-shelled chicken eggs from a local retail center, with an average weight of 62.39 grams, and excluded any showing cracks, shell defects, or surface contamination. The eggs were randomly divided into six groups: an uncoated control, eggs coated in pure 100 percent aloe vera gel, and four groups coated with aloe vera gel containing either 500 or 1000 parts per million of fennel essential oil or the same concentrations of lime peel essential oil. The essential oils were extracted by steam distillation using a Clevenger-type apparatus for three hours, following European Pharmacopeia guidelines, from dried Mexican lime peel and ground fennel seed. Each egg was dipped in its assigned coating for one minute, dried, dipped again, and dried once more before all samples were stored at 5 degrees Celsius for 30 days, with quality assessments performed on days 1, 15, and 30.

The choice of coating ingredients was far from arbitrary. Aloe vera gel is a transparent, viscous substance rich in carbohydrates, proteins, fibers, soluble sugars, vitamins, minerals, amino acids, organic acids, and phenolic compounds, and it has established antioxidant and antimicrobial credentials in food applications. Fennel essential oil, dominated by trans-anethole at roughly 65 to 78 percent of its composition, has demonstrated bacteriostatic effects against Escherichia coli, Bacillus subtilis, and Staphylococcus aureus. Lime peel essential oil is an even more complex mixture of more than 100 compounds, including limonene, citral, and linalool, and is prized for its potent antioxidant and antibacterial properties. By embedding these oils within the aloe vera matrix, the researchers aimed to create a coating that was simultaneously a physical barrier and an active antimicrobial delivery system.

The results on weight loss were striking. After 30 days of refrigerated storage, uncoated control eggs had lost 4.81 percent of their initial weight, while every coated group lost only about 3.35 percent, a roughly 30 percent reduction. The researchers attribute this to the formation of a semipermeable barrier on the shell surface that limits the diffusion of water vapor and carbon dioxide through the shell’s pores. Interestingly, adding essential oils provided no additional weight-loss benefit beyond the aloe vera gel alone, suggesting that the moisture barrier was supplied entirely by the gel matrix and that the oils’ contribution lay elsewhere, primarily in antimicrobial activity.

Internal quality told a similar story. The Haugh unit, the standard industry measure of albumen quality based on the height of the thick egg white, declined in all groups over the month, but coated eggs fared markedly better. Uncoated eggs fell from a Haugh unit of 76.21 on day one to just 54.17 by day 30, while eggs coated with aloe vera gel containing 1000 ppm of fennel essential oil retained a value of 65.74, and those with 1000 ppm lime peel oil reached 65.40. The mechanism is rooted in egg chemistry: as carbon dioxide escapes through the shell during storage, the albumen becomes more alkaline, protein structures break down, and the thick white thins into a watery state. By slowing carbon dioxide loss, the coatings delayed this alkalization and preserved the ovomucin network responsible for albumen viscosity.

The pH measurements reinforced this picture. Fresh albumen contains about 0.5 percent dissolved carbon dioxide, and its loss during storage can push albumen pH from around 7.2 toward 8.5 or higher. In this study, uncoated eggs climbed to an albumen pH of 8.26 after 30 days, whereas eggs coated with aloe vera gel plus 1000 ppm fennel oil reached only 7.60, and those with 1000 ppm lime peel oil reached 7.64. Yolk pH followed the same pattern, rising to 6.91 in controls but only to 6.54 and 6.57 in the highest-concentration fennel and lime peel treatments, respectively. Because yolk and albumen pH are both recognized freshness indicators, these numbers translate directly into longer commercial shelf life.

Functional properties also benefited. Albumen foaming capacity, which matters for baking and culinary performance, declined with storage in all groups, but coated eggs retained significantly more foaming ability than controls, with coated samples reaching about 7.5 milliliters of foam per gram of albumen at day 30 compared with 6.28 for uncoated eggs. The researchers explain that ovomucin stabilizes foam by forming insoluble films around air bubbles, and that coatings preserve this functionality by limiting the water and carbon dioxide losses that drive pH-driven protein degradation. Shell thickness, by contrast, was unaffected by either coating or storage time, indicating that the coatings act as surface barriers rather than altering the mineralized structure of the shell itself.

Perhaps the most compelling results came from the microbiological analysis. Total microbial counts rose in all groups over the storage period, but coated eggs consistently carried lower loads than controls. By day 30, uncoated eggs had reached 5.40 log CFU per gram, while eggs coated with aloe vera gel alone reached 4.67. The essential oil treatments pushed the counts down further still: 4.16 log CFU per gram for 1000 ppm fennel oil and 4.17 for 1000 ppm lime peel oil. The authors attribute this to a dual mechanism, in which the coating acts as a physical barrier against microbial penetration while simultaneously serving as a carrier for natural antimicrobial compounds. Aloe vera’s activity stems from anthraquinones, saponins, phenolics, and organic acids, while limonene and gamma-terpinene in lime oil disrupt bacterial cell membranes, and trans-anethole, fenchone, and methyl chavicol in fennel oil inhibit a wide range of pathogens and even biofilm formation.

The study does have limitations that the authors themselves acknowledge. Only two concentrations of each essential oil were tested, storage was confined to a single refrigerated condition for 30 days, and sensory properties and consumer acceptance of the coated eggs were not evaluated. Industrial scalability, long-term performance, and economic feasibility remain open questions. Nevertheless, the overall conclusion is clear: aloe vera gel enriched with 1000 ppm of either fennel or lime peel essential oil represents a promising natural coating for extending egg shelf life and maintaining quality during refrigerated storage. As food scientists worldwide search for alternatives to synthetic preservatives, this simple dip-and-dry treatment, built from ingredients with long histories of safe human use, offers an elegant demonstration that sometimes the best packaging material may already be growing in a garden.

Subject of Research: Edible aloe vera gel coatings enriched with fennel and lime peel essential oils for extending the shelf life and microbial safety of refrigerated eggs

Article Title: Enhancing the Shelf Life and Microbial Safety of Refrigerated Eggs Using Edible Coatings of Aloe Vera Gel Combined With Fennel and Lime Peel Essential Oils

Article References: Ranjbarinasab, Z., Shahdadi, F., Yousefi, M., Seyedimarghaki, Z., & Omidi, S. (2026). Enhancing the Shelf Life and Microbial Safety of Refrigerated Eggs Using Edible Coatings of Aloe Vera Gel Combined With Fennel and Lime Peel Essential Oils. Food Science & Nutrition, 14(10), Article e72389. https://doi.org/10.1002/fsn3.72389

Image Credits: AI Generated

DOI: 10.1002/fsn3.72389

Keywords: edible coatings, aloe vera gel, essential oils, fennel, lime peel, egg preservation, shelf life, microbial safety, Haugh unit, food science, natural preservatives, refrigerated storage

The review, conducted by Maryam Babar and Aymen Arain of the Edward Via College of Osteopathic Medicine and Nina Martins of Virginia Commonwealth University, synthesizes peer-reviewed literature identified through PubMed searches using terms such as cosmetic contamination, public testers, and pathogens in makeup. Rather than applying a formal systematic protocol, the authors took a narrative approach, examining studies of personal-use cosmetics, salon-shared products, preservative efficacy, and regulatory policy to build a comprehensive picture of what is, and is not, known about contamination in cosmetics that pass through many hands. Their central and most sobering finding is a gap in the evidence itself: no study to date has directly measured microbial loads or quantified infection risks from public makeup testers in retail settings.

What the surrounding literature does show is cause for concern. Studies of cosmetics in general use have repeatedly isolated opportunistic pathogens, including Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans, and various Bacillus species, from both personal and shared products. Alarmingly, contamination has been detected even in items that were still unopened, suggesting that manufacturing-stage contamination or compromised packaging can introduce microbes before a product ever reaches a consumer’s hands. Once products are in use, repeated contact with fingers, faces, and the environment introduces new organisms, and many formulations provide the water, nutrients, and neutral pH that microbial life requires.

The technical reasons why cosmetics can support microbial growth are well understood. Water-containing products such as creams, liquid foundations, and mascaras are particularly vulnerable, since moisture is the fundamental requirement for bacterial and fungal proliferation. Preservative systems are designed to suppress this growth, and regulatory frameworks in most jurisdictions require demonstrated preservative efficacy before a product can be marketed. However, preservatives are not infallible. Their effectiveness depends on concentration, formulation chemistry, and the size and frequency of the inoculum they face. A tester that is opened all day, handled by dozens or hundreds of people, and never sanitized may present a microbial challenge that overwhelms even a well-designed preservative system. Research on preservative systems has also shown that they can alter the skin microbiome itself, complicating the picture of how cosmetic formulations interact with the microorganisms that naturally colonize healthy skin.

The closest real-world proxy for retail testers comes from studies of communal cosmetic kits in beauty salons, and those findings are consistently troubling. Investigations of shared makeup kits in women’s beauty salons have documented high rates of bacterial and fungal contamination, with contamination levels notably higher in communal-use settings than in products used by a single owner. One study of salon cosmetics also assessed exposure to microbial metabolites, underscoring that the risks of shared products may extend beyond live organisms to the bioactive compounds they produce. In a salon, the shared kit is typically used by a limited and semi-stable population; a retail tester, by contrast, may be touched by an essentially unbounded stream of strangers, none of whom have any knowledge of the product’s handling history.

The clinical consequences of exposure to contaminated cosmetics range from trivial to serious. Opportunistic pathogens such as Pseudomonas aeruginosa can cause severe eye infections, including keratitis that threatens vision, particularly when contaminated products contact the eye area around mascaras, eyeliners, and eye shadow. Staphylococcus aureus can provoke skin and soft tissue infections and, in some cases, more invasive disease. Candida albicans poses particular risks to immunocompromised individuals. Perhaps most strikingly, a recent study found that makeup testers can act as reservoirs and transmission sources of antibiotic-resistant bacteria, meaning that a swipe of contaminated lip gloss could theoretically transfer organisms that are difficult to treat even when they do cause infection. For vulnerable users, including people with compromised immune systems, broken skin, chronic skin conditions, or recent cosmetic procedures, exposure to contaminated testers represents a heightened and largely unrecognized risk.

Despite this accumulating evidence of risk in adjacent settings, the review emphasizes that retail testers themselves exist in a regulatory vacuum. There are no mandated sanitation protocols for testers, no requirements to track how long a tester has been in use, no expiration tracking for opened demonstration products, and no microbial testing obligations. In contrast, finished cosmetics sold to consumers are subject to established safety and shelf-life regulations in Europe and internationally, including requirements for preservative efficacy and period-after-opening labeling. A tester on a store counter, which may be exposed to more microbial pressure than any personal product ever will be, is exempt from all of these protections. The authors argue that this asymmetry is difficult to justify from a public health standpoint and that testers may serve as unrecognized vectors for microbial transmission and infection.

The methodological gap the review identifies is as important as the contamination findings themselves. Because no studies have directly sampled testers in real retail environments, the actual magnitude of the risk remains unknown. Microbial loads on testers could range from negligible to dangerous, and without direct measurement, neither regulators nor retailers can make evidence-based decisions. The authors call for research to evaluate the safety of these products in real-world settings, including surveys of contamination across product types, store formats, and climates, as well as studies quantifying the transfer of microbes from tester to skin. Such data would provide the foundation for establishing evidence-based hygiene protocols, whether that means scheduled sanitization, single-use applicators, sealed sampling systems, automatic replacement intervals, or the retirement of open testers altogether.

In the meantime, the review has practical implications for consumers and retailers alike. Shoppers with cuts, active skin infections, recent procedures, or weakened immune systems would be prudent to avoid shared testers entirely, particularly around the eye and lip areas where the infection risk is highest. Retailers and cosmetics companies, for their part, could adopt sanitation and replacement practices voluntarily, and the authors argue that recognizing the clinical relevance of tester contamination is essential for guiding future policy, public health measures, and consumer education in cosmetic safety. As the beauty industry continues to grow and as awareness of microbiome science reshapes how consumers think about the products they put on their skin, the humble makeup tester, sitting open on a brightly lit counter, may come to be seen less as a harmless indulgence and more as an unexamined interface between hundreds of strangers’ microbiomes and every new customer who stops to try a shade.

It is worth noting the nature of the evidence base itself. As a narrative review, the article does not pool data or grade studies systematically, and the authors acknowledge that no formal inclusion or exclusion criteria were applied. This means the conclusions should be read as a synthesis of available literature rather than a quantitative risk assessment, which makes their call for direct sampling studies all the more pointed. The review also received no external funding, and the authors declared no conflicts of interest.

The cited literature adds several instructive details. Quality investigations of commonly used topical cosmetic preparations have documented contamination in products beyond makeup, suggesting the problem spans cosmetic categories. Work on preservative systems in full formulations has examined their in-vivo effects on the skin microbiome, while separate research has tested how chemical preservatives affect resident flora isolated from healthy facial skin, indicating that formulation choices shape not only microbial survival in the product but also the ecology of the skin it contacts. Even unusual organisms have surfaced: Vibrio metschnikovii has been isolated from cosmetic products and proposed as a potential cause of skin infection, illustrating that the range of contaminants is not limited to the familiar staphylococcal and pseudomonal species.

The timeline of the underlying research is also relevant. Much of the foundational work on in-use cosmetic contamination dates back well over a decade, while studies of salon-shared kits and antibiotic-resistant organisms on testers are more recent, suggesting growing but still fragmented attention to the issue. The review went through revision in August 2026 and was published in September 2026 in volume 318 of the journal, arriving at a moment when consumer interest in microbiome-aware cosmetics is rising even as the hygiene of the products consumers actually touch in stores remains unmeasured.

Subject of Research: Microbial contamination of shared makeup testers in retail environments and its public health implications.

Article Title: Beauty or biohazard? Microbial contamination in shared makeup testers and public health implications: a narrative review

Article References: Babar, M., Arain, A., & Martins, N. (2026). Beauty or biohazard? Microbial contamination in shared makeup testers and public health implications: a narrative review. Archives of Dermatological Research, 318(1), Article 404. https://doi.org/10.1007/s00403-026-04928-6

Image Credits: AI Generated

DOI: 10.1007/s00403-026-04928-6

Keywords: cosmetic contamination, makeup testers, microbial safety, opportunistic pathogens, public health, skin microbiome, hygiene practices, antibiotic-resistant bacteria, beauty salons, preservative efficacy, Staphylococcus aureus, Pseudomonas aeruginosa