What is a Microbiome Formulation?

Less is More approach
Statistically, Women typically apply around 16 beauty products each day, exposing their skin to about 515 synthetic chemicals daily. (“The Average Woman Uses 16 Beauty Products Every Day. Here Are the Ones Worth the Investment,” 2018) This extensive exposure has led to a rise in skin sensitivity, which now affects 60-70% of women and 50-60% of men worldwide (Sensitive skins wear their own skin microbiota, 2024) - a number that continues to climb. To mitigate these effects, experts advise using fewer, essential ingredients and prioritising simple, balanced formulations over emphasising single "hero" ingredients. This holistic approach fosters skin compatibility, supporting healthier skin with reduced risk of irritation.

Traditional vs Microbiome approach
The traditional skin care approach highlights a single, "hero" ingredient or a blend of active ingredients to deliver specific benefits, with the spotlight on these components as the main drivers of product efficacy. However, a microbiome-focused approach takes a broader, more holistic perspective. It considers how each ingredient, including non-active additives (functional ingredients), interacts with the skin and its microbiome. This method aims to create formulations that support the skin's natural microbial balance, ensuring that every component contributes positively to overall skin health.

Anhydrous Products
Anhydrous products, with no water, do not require preservatives since bacteria need moisture to grow. However, they face challenges: incorporating water-soluble actives is difficult, and they are more prone to oxidation and rancidity. Their thick, oil-based consistency may also not suit all skin types, especially oily or sensitive skin. Despite these drawbacks, anhydrous formulations appeal to consumers interested in preservative-free, minimal skincare.

Water-based Products
Water in skincare products often makes up 80%, requiring emulsifiers to mix with oils and preservatives to prevent bacterial and fungal growth. To avoid contamination, effective preservation is essential. Instead of skipping preservation, reducing water activity can enhance product stability by limiting moisture, which is crucial for safer, less chemically intensive formulations.

pH
Maintaining a skincare formulation with a slightly acidic pH, ideally below 5, supports the skin's microbiome and barrier function. Alkaline cleansers with pH levels above 7 can disrupt the acid mantle, weakening the barrier and encouraging harmful bacteria. Hülpüsch et al. (2022) found that a higher skin pH (5.7–6.2) in atopic dermatitis patients is linked to increased Staphylococcus aureus colonisation, worsening inflammation and barrier issues. Acidic formulations may help control bacterial overgrowth, reducing flare-ups and promoting skin health in at-risk groups like those with AD.


Ingredients
Formulations that are high in lipids can strengthen the skin barrier, enhancing hydration and resilience against irritants. Combining gentle surfactants with super fatty agents further reduces potential for irritation and maintains moisture, which is particularly beneficial for sensitive skin types. These principles help prevent disruption of the microbiome, ensuring the skin remains balanced and resilient over time (Van Belkum et al., 2023). The selection of mildly acidic, pH-balanced ingredients close to the skin’s natural acidity (4.7 < pH < 5.7) is crucial, as it helps preserve the skin’s barrier and microbiome.


Preservatives
To protect the skin microbiome and reduce bacterial growth, it’s essential to minimise preservatives, especially in oil-based products. Anhydrous formulations, which don’t require preservatives, are ideal when possible. For water-based products, alternatives such as antimicrobial peptides (AMPs), and natural humectants like glycerin, sodium lactate, and NMF components (ceramide, urea), can improve microbial stability and skin barrier function (Halla et al., 2018). Airless packaging and sterilisation methods like UHT technology can further enhance product safety by minimising contamination, reducing the need for traditional preservatives.

Surfactants
Water-in-oil System:
Choose emulsifiers with a low hydrophilic-lipophilic balance ratio and natural ingredients like plant oils or sugars. Limit emulsifier concentration to maintain skin barrier integrity. Avoid Polysorbate 80, which can promote pathogen growth, and use alternatives like Polyglyceryl 4 Oleate, which self-emulsify when mixed with water.

Oil-in-water System:
Use microbiome-friendly emulsifiers derived from natural sources like plant oils and sugars. Examples include Olivem 1000, made from olive oil (Cetearyl Olivate and Sorbitan Olivate), and Emulium Mellifera MB, which combines beeswax and jojoba wax (Polyglyceryl-6 Distearate and Jojoba Esters). These emulsifiers help maintain skin health while supporting the microbiome. It's also important to limit the concentration of emulsifiers to avoid disrupting the skin barrier.

Fragrances/Essential Oils
Fragrances should generally be avoided in skincare formulations, especially for sensitive skin, as many fragrances can cause irritation. However, certain essential oils may serve as antimicrobial agents in products for non-sensitive skin, offering a natural alternative to synthetic preservatives. For instance, bergamot and lavender oils demonstrate antibacterial and antifungal effects, particularly against Staphylococcus aureus, though they do not affect S. epidermidis (Kim et al., 2022). Additionally, rosemary oil and phenylethyl alcohol show strong antifungal properties, adding preservative benefits without traditional preservatives.