In one of the chats, there was a discussion about how essential oils are tested not just from season to season, but sometimes even with every new batch. This gave me the idea to write about how plants actually react to the weather and how this can affect us, cosmetic formulators. And this applies not only to essential oils, but to others as well. Will the composition of the same oil differ depending on the year, and what is actually happening inside the plant cells? And why does it happen?
We all love natural oils. Apricot kernel, flaxseed, sweet almond! I don't know a single home formulator who doesn't use oils in their cosmetics. Vegetable oils and essential oils are the cornerstones of natural cosmetic formulations. But their composition — in particular, the types and ratios of fatty acids and volatile compounds — is not fixed. Environmental conditions during the plant's life cycle directly affect the quality, function, and stability of these botanical ingredients.
In this article, we will examine how temperature, sunlight, humidity, and other weather-related variables affect the fatty acid profiles of common oils and the composition of essential oils.
Every plant adapts to its environment and tries to survive in any situation. Nature is very clever and has provided for almost everything. Except, perhaps, for human stupidity (a bit off-topic, but I couldn't help myself — no one is safe from that, including poor plants!).
Fatty acids and temperature
So, in the same plant, depending on the year, a cold climate leads to a high content of unsaturated fatty acids (e.g., linoleic, linolenic acids) to maintain membrane fluidity. Conversely, a hot climate increases the content of saturated fatty acids (e.g., palmitic, stearic acids) for membrane stability.
Factor | Cold climate | Hot climate |
|---|---|---|
Type of fatty acids | ↑ Unsaturated (linoleic, linolenic) | ↑ Saturated (palmitic, stearic) |
Why the plant needs it | Membrane fluidity at low t° | Membrane stability at high t° |
For cosmetics | More Omega-3/6, absorbs more easily | Denser texture, longer shelf life |
Sunlight and oil yield
High levels of sunlight increase oil yield but can lead to a shift in fatty acid composition towards more stable forms. Cloudy conditions can reduce total oil content but increase polyunsaturation.
Moisture and drought
High rainfall can lead to a decrease in oil yield and a decrease in polyunsaturation, while drought stress often increases oleic acid content.
Drought stress is not just a bad thing. For a plant, it is a signal to accumulate oleic acid (Omega-9), which is more resistant to oxidation. Such oil has a longer shelf life and is more stable in cream formulas.
Wind and altitude
Wind and altitude alter temperature and moisture exposure, indirectly influencing fatty acid biosynthesis. Plants at high altitudes tend to produce oils with a more complex and interesting profile.
Essential oils and the weather
Essential oils are highly reactive to climate changes due to their role in plant protection.
Sunlight
Enhances the production of monoterpenes and antioxidant compounds.
Humidity
Promotes the synthesis of antibacterial and antifungal volatile substances: thymol, carvacrol, eugenol.
Cold
Favours sesquiterpenes and oxygenated compounds, such as linalool. Oils become more “deep” and complex.
Heat
Increases overall yield but can simplify oil profiles — less diversity of components.
Drought vs precipitation
Moderate drought increases oil concentration — this stress on the plant triggers the production of volatile compounds, while excess rainfall can reduce quality and yield.
Altitude and wind
High altitude and wind result in more potent essential oils with sharper and more aromatic profiles. Mountain lavender, for example, is valued higher than lowland lavender for this very reason.
Why does this matter to us, as formulators?
Knowing how climate affects plant oils helps us choose the right batch or region to achieve target effects.
Flaxseed oil from a cool region
Higher Omega-3 content, but a shorter shelf life. Ideal for anti-ageing products, but requires antioxidant protection.
Peppermint grown in drought
Higher menthol content. A more pronounced cooling effect in products.
Oregano grown in high humidity
More carvacrol — better antimicrobial effect. Valuable for preservative and therapeutic formulas.
Environmental conditions are not just background variables. They actively influence the chemical composition of plants. Understanding their role allows us to formulate with greater purpose and precision, creating cosmetic products that are not only natural but scientifically optimised.
Read also: Polymorphism of butters • Oils and butters by skin type
Oksana Walker
Cosmetic chemist, founder of the Walker Formulation Academy
IFSCC • SCS • IAA • IAC
