Essential oils are are some of the riskiest ingredients in DIY skincare, and most people don’t realise it because of all the misinformation out there. There’s this idea that they’re safe and simple to use because they’re all natural, but unfortunately, that’s not the whole story. Mis-use of essential oils can lead to everything from irritation to rashes to severe chemical burns. Using them properly is, well, essential.

In this post I’m going to share five dangerous essential oil myths that most new makers—and many more experienced ones, too!—make, and how to avoid them so you don’t hurt yourself, your friends, or your customers. I made all of these mistakes when I first got started, and not understanding myth/mistake #4 early enough has had life long consequences 😭 I really want to save you that pain.

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As you’re reading you might be thinking “hey, I’ve been doing that for ages and nothing has gone wrong, so how bad can it be?”—but some of these mistakes won’t backfire the first—or even the fortieth—time. But when they do backfire, it can be bad. Want to see some examples of just how bad it can be? Check out the Adverse Reaction Reports database on the Tisserand Institute website. There’s some scary stuff in there.

What are essential oils?

Essential oils are highly concentrated, fragrant, naturally occurring ingredients made from plant material like seeds, petals, peels, and barks. We use essential oils to scent our DIYs and potentially add some lovely aromatherapy and skincare benefits, too.

They are really interesting, complex ingredients that are comprised of lots of different aromatic chemicals like linalool, limonene, menthol, benzyl alcohol, and geraniol. Yes, chemicals! Essential oils are made of chemicals, just like everything we eat, drink, and interact with.

Now, it’s easy to think that essential oils are, well, oils. It’s right there in the name, after all! While it’s true that they are oil soluble—they mix readily with oils—essential oils are not actually oils. True oils like almond oil and sunflower oil—often called carrier oils—are made of fatty acids like stearic acid and oleic acid, while essential oils are made of potent, non-fatty aromatic chemicals.

The most common newbie mistake

This mistake is super duper common. I definitely did this when I first started, and I still see it all over the internet and in books.

At best, this will create inconsistently scented products, and at worse it can cause serious skin issues.

So: imagine your friend gives you their famous cookie recipe, but all the measurements are in ‘handfuls’. You make it as written, but it totally flops. Gah! Now, of course, you’d never bake by the handful—but you’re doing something similar if you measure your essential oils by the drop.

Just like the size of your handful will be different than your friend’s due different sizes of hands and different grip styles, a “drop” can vary a lot depending on factors like the specific essential oil, the bottle it’s being ‘dropped’ out of, and ambient temperature.

Essential oils are really potent, so measuring them accurately is essential to ensuring you’re using them safely. For true accuracy, you need to use a precise scale to weigh out your essential oils, not count drops. This is always important, but becomes more important as you scale your formulations up to sell or gift.

I recommend purchasing a scale that can measure to two decimal points of a gram; I’ve shared some recommendations that start around $20USD in the free Humblebee & Me DIY Encyclopedia entry on “precision scales”.

The swap flop

This second mistake can be an easy recipe for serious skin irritation, even if you’ve weighed out all your essential oils.

If you’ve been DIYing for longer than about a day, you’ve definitely come across a formulation that called for an ingredient you don’t have and wondered “what can I used instead?” If that ingredient is sweet almond oil, swapping it for apricot kernel oil won’t make much of a difference. But, if that ingredient is an essential oil, what seems like a simple swap can completely ruin your final product.

Imagine you were cooking up a batch of chili, and the recipe called for “1 tbsp sweet paprika”, but you didn’t have paprika, so you decided to use a tablespoon of cayenne pepper powder instead. They’re both spices (and spices made from a type of pepper, at that!), so a one-for-one swap should be fine—right?

As I’m sure you’ve already worked out, that swap would make for a batch of chili that’s hotter than magma—and nothing like what the original recipe intended. That’s because, even though they are both “spices”, the composition of paprika and cayenne pepper are really different.

The same is true for essential oils. They are complex, highly varied blends of natural chemicals. Different chemical constituents have different safe usage levels, so the safe usage level of every essential oil varies with its precise chemical composition.

This complexity further compounds when multiple essential oils in a blend are sources of the same limiting chemical constituents. This means you could use a safe level of two or three different essential oils, but exceed the safe usage level of some of the chemical components found in those essential oils, therefore exceeding safe usage levels for your entire product 🙁

Autumn 2023: If you'd like to try out Formula Botanica for free, they're offering a no-cost formulation masterclass where you can learn even more about formulation + test out their teaching style! You can sign up here 🙂 I highly recommend it ❤️

Feet are feet (not eyes)

This next mistake is sort of an extension or variation om the previous one.

Just can’t treat all essential oils the same, we also can’t treat all products the same when it comes to adding essential oils. This is essential if you’re planning on selling your products—especially in the EU, where regulations are much tighter than they are in the USA and Canada.

Different product types have their own safe usage levels, and those product types and usage levels are dictated by the International Fragrance Association. An eye cream, for example, has far lower maximum safe level of essential oil than a foot cream.

So, just because a certain percentage of essential oil might be safe in one sort of product, you can’t assume it’ll be safe in another sort of product (especially if you’re going from categories with generally higher usage levels, like wash-off and body products to ones with generally lower levels, like leave-on and facial products).

Like milk, not wine

Our next mistake is one that’s really close to my heart as I’m still suffering from the effects of it myself, and I will for the rest of my life.

You might’ve read that high quality essential oils don’t—can’t—expire. I’ve seen this myth a lot, often perpetuated by those involved with essential oil MLMs.

This is flat out wrong. Essential oils are natural products, and like many natural products—fresh produce, milk, and carrier oils—they change over time. While some essential oils improve with age (patchouli is a great example), many more degrade.

The scents of essential oils change as they break down, and they oxidize, creating morphed chemical compounds that can be bad for the skin, increasing the chance of negative reactions and sensitization.

Using old lemon essential oil is the reason I can never use citrus essential oils topically again, even though I love them. I developed a sensitivity to citrus essential oils years ago, and now everything from grapefruit to lime to orange essential oil makes me really itchy.

My biggest tip for preventing the use of old, expired essential oils it not to over-buy. I know it’s really tempting to buy bigger bottles of essential oils because the cost per mL is always lower (I definitely did this when I first got started—the bottle of lemon essential oil that caused me to become sensitized was a whopping 500mLs), but the bigger the bottle, the longer you’ll have it. And the longer that bottle lasts, the higher the chance that it’ll oxidize before you’ve finished using it up.

While oxidization isn’t a very fast process (Tisserand says “Most essential oils keep well for at least 1-2 years before oxidation starts to take effect.”), buying bottles than you can’t easily finish in 6–12 months asking for oxidized essential oils, wasted money, and potentially lifelong skin sensitization.

P.S. Store essential oils in the fridge to extend their shelf life!

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Ok, so… how much can I use?

Given all the different variations of essential oils and product types out there, you can see that “rules of thumb” aren’t super useful when it comes to essential oils. They’re often a good starting point to ensure you’re in the right ballpark, but for precision, you need to look up each and every essential oil you want to work with in the context of the formulation you’re looking to include it in.

That’s a bit of an involved process, so I’ve detailed how to do that in a post entirely dedicated to that. Click here to check it out!