One of the things I see a lot online and on my travels is people adding water to essential oils to make blends and preparations. The trouble with this is that essential oils are hydrophobic. That means that they do not disperse in water and just glob together so the risk is that stronger oils will be more likely to irritate as they are not being quenched and the blend is not going to be evenly distributed. The other factor to consider is that water goes mouldy very quickly and without a preservative, you are bringing a lot of contamination into your product.
One solution to this is to blend directly with hydrosols or carrier oils depending what you are making. Hydrosols such as mint and Rosemary make fantastic bases for mouth washes and toothpastes if you are making your own. Sage and Mugwort hydrosols make good bases for smudging sprays and if you are making preparations for the skin and hair then gentler hydrosols such as nettle or willow are perfect.
Hydrosols have their own preservatives, their own properties. Nettle, for example is highly astringent and toning for skin as well as being anti-inflammatory. Essential oils are dispersed evenly into hydrosols so it is worth blending them into a small amount even if they are simply being added to the bath.
I sometimes get asked as well why is a hydrosol better than an infusion? Hydrosols contain distilled plant waters so they are much purer and they also contain traces of essential oil so their therapeutic benefits are much more profound. And yes, they do enter into the skin so it is worth getting all the goodness available to you. All of our hydrosols are wildcrafted and organic so we bring as much as the plant medicine as possible to your products.