There’s a hot topic of late in the aromatherapy community. Baths are hot, baby! Specifically, aromatic therapeutic baths. Winter and cold brings out the bather in everyone. Aromatics and therapeutics are a desirable addition to make the bath experience wonderful and beneficial. The way most people include them in their bathing ritual and what’s been the norm practiced in the aromatherapy community for many years is to either drop a few drops of essential oil in the bath water or to mix them into a cup or so of sea salt or epsom salt, with or without additional ingredients, dump that in the tub and slide into the water. While many have taught these two methods are THE way to get a nice aromatherapeutic bath for many years, there’s just one teeny tiny little problem with it. It’s not really the safe.
Wait! I knew just dropping essential oils into the water was a No-No because oil and water don’t mix. But are you saying bath salts made with essential oils are not safe? Yes, if they are made like described above, that’s exactly what I’m saying. Not using the correct medium for aromatic baths with essential oils can leave you with hot cross buns and tingling ta-ta’s. That’s not as appealing as it sounds, people. Trust me on this. Been there and done that! Paid the price for my ignorance.
It’s actually simple chemistry. The aromatherapy community is slowly learning the old ways that have been taught are not necessarily good or safe. Most within the greater aromatherapy community are catching up with learning better options. This is wonderful news! But, with so much on the internet that is inaccurate which many latch on to and follow, we need to get the word out a little farther and faster to help reduce the risks of being injured in the bath from essential oils being used unsafely. So let’s talk about the what and why of safe aromatic baths with essential oils and clear up some confusion about terminology while we’re at it.
Why are salts not a good medium for incorporating essential oils into bath water? Salts are comprised of polar molecules and are water soluble, which means they dissolve in water (also polar) and mix with it on a molecular level. Whereas essential oils are non-polar, oil soluble and will not “dissolve” in water. Polar molecules and non-polar molecules repel each other, much like the polar and non-polar sides of magnets will resist each other. When you try to mix polar and non-polar…they don’t like each other so they won’t embrace and bond. Secondly, salts are not a dispersant, solubilizer, emulsifier, surfactant or diluent. They are “an additive”, meaning they are added to something in small quantities, in this case, a tubful of water. As a side, ingredients such as baking soda, citric acid, corn starch, root powders, and similar are also additives and do not work to incorporate essential oils into the bath safely.
Here’s where it gets tricky. How can we safely include essential oils in the bath? Well, there are a number of ways to include them so you can enjoy the aromatics and therapeutics and still not burn your bum. Take notes, enthusiasts. Class is in session. This is a longer lesson because to explain it all in one place in even the limited ways for better understanding and safety practices, it has to be. So don’t fade out on me. I’ll hit the high points and simplify as best I can.
Diluents? Dispersants? Surfactants? Solubilizers? Emulsifiers? Additives? All terms and product classifications you may see tossed around. But exactly what are they and can you use these for that lovely essential oil infused bath? First, let me make this as clear as I possibly can. Although there is some crossover between a few of these, they are all different substances and compounds with different functions, actions and purposes. Not all can or should be used in a bath to safely incorporate essential oils. These are also some of the “terms” which have a lot of confusion attached to them because people have possibly heard them but don’t actually know what they are. You see, they are scientific/chemistry terms, often used in cosmetic and product formulation circles, but they are not necessarily “aromatherapy” terms. But, with the growing popularity of Pinterest and so many do-it-yourself enthusiasts now finding and frequenting cosmetics and soap forums, where they may hear or see these similar but different terms/product classifications, they have begun crossing over into the greater aromatherapy community. Unfortunately, they are often getting used errantly or interchangeably. This is causing more confusion as well as spreading misinformation. Let’s remedy that a tad, shall we?
What is a diluent? We all know that a diluent (sometimes referred to as a dilutant) is a substance that when mixed with another like substance, weakens the concentration of that like substance, diluting it, right? OK, if you didn’t know that, you do now. Water added to juice dilutes the juice. Juice added to gin dilutes the gin. Fats, specifically lipid rich fixed oils, would be a diluent for another oil, in this case, essential oils, which are volatile oils without lipids but still oils by definition because they are hydrophobic. Both the fixed oil and the essential oil are non-polar meaning they both are still repelled by the polar water molecules and will not bind with the water. They will float on top of the water’s surface or sink to the bottom of the contained water instead. But now, the concentration and potency is reduced so it’s not undiluted direct skin contact and thus safer, providing it’s properly diluted. A high fat milk or cream can also act as a diluent that will have a semi-emulsifying action (Read more on that in the emulsifier section) along with a diluting action and sometimes, a minor foaming action if agitated. So diluents in the way of a fixed oil or high fat content milk or cream are a fairly good choice for adding essential oils to baths.
What is a dispersant and what does disbursement mean? Well dispersing/disbursement means “to scatter into smaller size, number or amount into many directions”. (Ex. “The crowd dispersed after the concert was over.”) In chemistry, dispersants are a liquid or gas, which scatters and breaks up another liquid or gas into smaller sizes. The appropriate dispersants can break up a non-polar hydrophobic substance into minute micro-sized droplets, scattering them into the a polar, hydrophilic host solution, where they hang out in suspension looking for a compatible lipid to bond and join up with again. These micro-droplets are so small that they may be difficult to see. How do they do this? The molecules of a dispersant have a water-loving end and an oil-loving end. One end grabs onto a water molecule, while the other end grabs onto an oil molecule, becoming a “tie”, between the two, breaking the surface tension and scattering the essential oil into the water in tiny micro-droplets. Dispersants alone are not the optimal medium for adding essential oils to the bath. Because dispersants are usually single action substances that simply scatter the dispersed substance into smaller, less noticeably parts of itself, the essential oils are still in 100% concentration, still non-polar, and still looking for a lipid to bond with. The essential oils are still repelled by the polarity of the water molecules and still result in undiluted skin contact, where it will find the lipids it seeks to bond with. The only difference is now, the essential oils are in micro-droplets spread over a larger area instead of larger, more visible drops in smaller areas. This means more skin area to come in contact with and bond with the lipids in skin. That’s not really ideal for a safe bath and has resulted in skin irritation. Dispersants usually need something added with them for them to be a very good and safe option to be used in baths. Oftentimes, dispersants on the market to the common non-professional consumer may include a surfactant, typically in the form of a detergent, which is intentionally added to create better surface tension, a longer lasting dispersing action and cause a suspension in the host solution. This is a good thing but even with the surfactant addition in the dispersing product, we often find that a little additional coaxing to combine in the form of another medium used with a dispersant may be needed. That may mean additional surfactants, a dilutent or even a solubilizer to create a multi-action, multi-function medium. The viscosity and density of the essential oils come into play and simply using a dispersant to add essential oils to a bath or soak is not always ideal.
What is a surfactant? A surfactant, derived from the words “surface active agent“, is a substance/compound which are made up of molecules that have a water-loving head and a fat-loving tail. This allows them to reduce the surface tension (or interfacial tension) between two liquids or between a liquid and a solid. Surfactants may act as detergents, wetting agents, emulsifiers, foaming agents or dispersants and combinations of these at times. Bar and liquid soaps, washes, shampoos, bubble baths and detergent based cleansers are examples of finished products which act as surfactants or have known surfactants intentionally added to the formulation. Their molecular structure and the way they break surface tension is actually how they clean. Because of this surface tension interruption, they can help disperse and suspend essential oils and even fatty oils throughout the host solution and have a small emulsifying action. Did you read the above about dispersants? If not, go back and read it. I have a hypothesis that because soaps, washes, shampoos, bubble baths and detergent based cleansers usually also contain at least one fatty oil, often with some of he fat from the oils used being what we call “free fats”. This means they have not been saponified during the soapmaking process and are available for the essential oils to bind with, giving a little bit of dilution of sorts. Soap aside, Polysorbates act as surfactants as well as acting as solubilizers in water. Milk powders, bubbling/foaming agents such as SLSA (Sodium Lauryl Sulfoacetate) and similar can also act as surfactants for the aromatic bath. But they may require additional ingredients to work in conjunction with or need manual manipulation to function in this capacity at the safest level for using essential oils in the bath. Surfactants also often act as emulsifiers and co-emulsifiers in certain cosmetic formulations such as multi-phase products. Yeah, I know, We’re getting into more complex and details areas here so moving right along.
What is a solubilizer? A solubilizer is a substance, known as a solvent, that completely dissolves another substance, known as the solute, making them one homogenous solution that’s actually bound together on a molecular level. It literally changes the molecular structure and solubility of a substance. Because of how they work, which is too much to get into right now, a solubilizer forces a once hydrophobic, not soluble in water bases solute to become hydrophilic and soluble in water bases. Solubilizers basically allow us to mix a small amount of oil in a larger amount of water base. They are, however, limited in that they can only “hold” and dissolve so much essential oils or fragrance oils by ratio. So it is possible to use too much essential oil and not enough solubilizer, resulting in part of the essential oil not dissolving and remaining non-soluble in water. In this case, what a solubilizer doesn’t dissolve will settle out and be separate, not homogenizing with the solubilizer and host substance. Polysorbate 20 and 80, Solubol, grain alcohol with very high ethanol content and similar are solubilizers often used to dissolve and incorporate an essential or fragrance oil into a water base to create a homogenous solution. This makes them an excellent solution for incorporating EO’s into a bath safely without much if any other additions and actions.
What’s an emulsifier? An emulsifier allows us to combine an oil base and a water base to create an oil-in-water or water-in-oil mixture that is an entirely different product….in texture, viscosity and appearance as well as function. Emulsifiers disperse and suspend oils into water but in a much more fine-tuned, precise and substance changing way than a dispersant does and with much smaller micro-droplet formations. Emulsions usually require sheer force action to get those molecules to hold hands tightly and stay together. They are designed to mix a large amount of oil into a water base whereas, as discussed earlier, dispersants mix a small amount of oil into a large water base. For example, lotions and creams are emulsified products, having a water phase and an oil phase with a relatively high percentage of oils (in double digits) to water. Emulsifying Wax NF and BTMS are common all-in-one emulsifiers used in cosmetics. In general, all-in-one emulsifiers, are not going to be a viable solution for using essential oils in the bath because (1) they are for creating emulsions and products such as lotions and creams (2) as part of how they work, sheer force is required to create an emulsion that stays emulsified (3) they also act as thickeners which is not something we want in the bath. However, a simple emulsifier combined with a solubilizer or dispersant may give multi-action to form a better distribution of the essential oils in the water or create a bond with the water molecules. An interesting nugget of information for you. Milk is a naturally occurring emulsion and actually where the word “emulsion” comes from. Therefore, a high fat milk or cream can be used as a simple emulsifier for some emulsification action to a certain degree.
- Water is made up of polar molecules. Essential oils are made up of non-polar molecules. The two do not get along and will run from one another at every opportunity without a mediator to make them sit together and play nice.
- Salts (sodium chloride, magnesium sulfate, sodium bicarbonate, etc) are additives much like botanical materials are. S alts are also polar, just like water. Because they are water-soluble, they dissolve/melt in water, becoming intimately intertwined with it. They are not an appropriate or safe medium for mixing essential oils in water.
- Emulsifiers, specifically all-in one emulsifiers, generally do not work to incorporate essential oils into water in a cohesive manner for baths and soaks. This is not their function or playground. They can, however, be combined with a surfactant and/or dispersant to give a more satisfying oil and water mix that is safe for baths and soaks.
- Dispersants scatter and suspend one substance in another. Alone, they are not necessarily the best or safest choice when it comes to adding essential oils to the bath for several reasons. While they are converted to micro-droplets and scattered out in the water, the essential oils are still 100% concentrated and undiluted, still non-polar and still do not mix with the water which is polar. They will seek out lipids to hook up with. Those lipids will be found in your skin. Although not the best option, using a dispersant can still be a viable option for aromatic baths or soaks simply because the scattering and suspension of the essential oils is done in micro-droplets so you get wide-spread coverage over the skin instead of localized exposure. You just need to know what to use and how to use it to achieve the highest safety possible. That may mean combining with surfactants, diluents and/or simple emulsifiers for a safer and satisfying aromatic bath.
- Surfactants break the surface tension of two liquids or a liquid and solid. Different surfactants behave differently at different percentages and may act as dispersants, detergents, emulsifiers or wetting agents. Soaps, shampoos and bubble baths are surfactants that, when combined with essential oils, allow them to incorporate more efficiently in the water because they also carry some emulsion and diluent action. They are a relatively safe option for incorporating essential oils in baths.
- Diluents with fat content weaken the concentration of essential oils, i.e,., dilute them. They are a wonderful option to indulge in a fragrant aromatic bath with the added benefit of moisturizing and softening skin. Yes, the fatty oil with essential oils will float on the water’s surface or they may sink to the bottom and line your tub, but if you dilute properly, this is not a concern. It’s no different than rubbing a properly diluted solution on your skin. You don’t need a lot of oil in the tub to do the job. A teaspoon or two with a 0.25% up to 5% dilution for the essential oils is enough. Please stay within safe dermal rates for every essential oil you choose to use. You will want to take precautions to avoid injury or falls from slippery surfaces, but one should take precautions in the tub anyway because even water or soap can make a mirror smooth surface slippery.
- Solubilizers will “dissolve” essential oils, creating a homogenous substance that is now water-loving and soluble in the water, allowing them to marry and become a blended family. They are an excellent choice for safely adding essential oils to bath water.
In conclusion, here’s my best assessment for how to safely add essential oils in the bath based on what I know and have researched extensively. Solubilizers are the best and safest option to use so using Polysorbate 20 or Polysorbate 60 and Solubol would be my recommendation. This is followed by using a diluent, diluting the essential oils with a light-weight fixed oil and/or a high fat content milk or cream. Next would be surfactants such as liquid soaps, bubble bath, shampoo or a mild detergent based cleanser. They work very nicely to allow us to safely add essential oils in bath. This would be followed by dispersants. There are so many dispersants I can’t list them or recommend one nor what they would best be paired with to be safe and effective. And last would be most emulsifiers, which are not going to be helpful for this application for the most part.
With any of the viable options, you can still add your bath salts for the extra oomph of therapeutics and indulgence. You can combine several of the options if you like. This is my preferred method personally because I’m a bath girl who loves a good luxurious bath with many benefits, including aromatic therapeutics. I love to indulge in an aromatic milk bath (I usually use a full fat buttermilk) that has big fluffy movie-worthy bubbles, my own exclusive salt soak blend and a little fixed oil to moisturize my skin, maybe a bag filled with herbal bath tea on occasion. I only use a little fixed oil though because it does reduce bubbles and lather. And I love my bubbles! Just remember to keep your amount of essential oil in a safe dermal range. More is not better with aromatherapy. In fact, the least amount you can use and still get the effects intended, the better off you will be. And if it’s just the aromatic scent of the essential oils that you’re after and not any skin benefit or all this seems overwhelming to you, just diffuse your oils while you soak in your lovely salty, bubbly, herbally bath. Easy peasy and best of both worlds, right?
Remember I said at the beginning of this article that aromatic baths and how to do them safely is a hot topic in the aromatherapy community lately? Well, as I was preparing and writing this article, our friend and colleague, Marge Clark of Nature’s Gift Aromatherapy had a similar idea and was writing a wonderful article about the changes that have occurred in recent times with aromatherapy, safety information for usage such as aromatic baths and more. I encourage you to read it. Marge has a way with words that makes reading fun and informative.
EDIT (May 15, 2017) – I need to clear up a mistake in this article that’s causing some confusion and misinformation to be spread. When first writing this article, in the conclusion, I inadvertently said polysorbate 80 is one option we can use as a solubilizer when including essential oils in the bath. That was a typo I didn’t catch when proof-reading before publishing and is incorrect. It should have said polysorbate 60. Polysorbate 80 is not an appropriate solubilizer for volatile oils and is much better suited for solubilizing fixed fatty lipid oils into water/water equivalents. Of all the polysorbates, polysorbate 20 is more aptly suited to use with essential oils and fragrance oils, while polysorbate 60 works well with both volatile oils and fixed oils. Of those specific three polysorbates, opt for polysorbate 20 to use with the essential oils as it’s more readily available and is specifically for incorporating volatile oils into a water base. I’ve corrected typo in the text above and apologize for any confusion or misinformation my mistake facilitated.
I must also clear up some confusion in another area because the info in this article is being used as reference for other products and uses when questions about how to incorporate essential oils or fragrance oils into water bases (such as body or air sprays) are being explored. I stated above that some ingredients cross-over into other ingredient designations (surfactants can be/act as emulsifiers or dispersants, for example). This all depends on the intended function, the specific action desired and required and the product formulation itself. One ingredient or substance may counteract, deactivate or cause a chemical reaction when combined with another. The details and schematics of this particular topic (product formulation) are far too in-depth and broad to get into and explain adequately in a blog post (or Facebook group post). These are not DIY/home crafter subjects that one can skim over and give simple answers to. Nor is it a “short lesson” with quick universally black and white answers, which is what many are wanting. I realize may want to “make it themselves” for whatever reason. But let me be very clear here. We’re talking chemistry and product formulation here which is NOT the same as a DIY home crafting project. The differences between product formulating and home crafting are vast, deep and wide. For comparison’s sake, those differences would be similar to using a first aid kit to attend to a minor scratch, scrape or bruise vs. performing major surgery. Some things are just not easy topics and are NOT going to be learned without extensive study, research and experience. Nor can they be addressed or taught in social media forums or through a single blog post.