Cilantro Oil Bath Salts and Sugar Scrub: The Maths

Most bath salt recipes tell you to stir essential oil into salt and tip it in the tub. The Tisserand Institute's bath safety article says the opposite in plain words: "Salt is not a carrier for essential oils." For a strong-smelling aldehyde oil like our cilantro leaf oil, that matters, and the sugar scrub is the easier project of the two.

Cilantro Essential Oil bottle

Cilantro Essential Oil

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What actually happens to oil in a bath

Tisserand's article describes oil poured into a tub as "a film of undiluted essential oils sitting on top", much of which then "is now attached to your skin" as you get in, and warm water keeps it from evaporating so it can sting. A vegetable oil carrier does not fix this by itself, because carriers do not disperse in water either; the article says they float and cling to the tub sides and your skin. Mixing the oil into a carrier first helps only until the salt hits the water, and then the oils float again. It also reports that baking soda, milk, glycerin, witch hazel, alcohol and aloe do not disperse oil.

The ones it does name as dispersing oil are Solubol, polysorbate 20, polysorbate 80 and Natrasorb. Its quantities, which we are reporting, not testing: 5 to 20 drops of essential oil per half ounce (1 tablespoon) of a household bath base; for polysorbate 20, 5 to 20 drops mixed with an equal amount of polysorbate for a bath; polysorbate 20 is "not suitable for carrier oils." We sell none of these, only the one oil, so this is where you buy a dispersant from a cosmetic ingredient supplier and read its own datasheet.

Decide: bath or scrub

If you do not want to buy a dispersant, skip the bath. A sugar scrub is a rinse-off product where the oil is already blended into a carrier, so it avoids the floating-film problem. It brings its own problem: you rub it onto skin, so the percentage matters more than in a tub.

The scrub arithmetic

Our shop page gives 0.5% to 2% in a carrier oil, roughly 3 to 12 drops per ounce. That implies about 20 drops per millilitre (3 drops is 0.15 ml, 0.5% of 30 ml). The Tisserand dilution page gives a higher band, 2% to 4%, for baths and wash-off products, and says its drop conversions "are always approximate". Those two sources disagree on the ceiling. We take our own lower figure because our oil's own page says decanal and its relatives dominate the aroma (the Certificate of Analysis on the shop page has the numbers, which we do not quote), and because a scrub is rubbed in for a minute, not rinsed off instantly. That is judgment, not a measurement.

A worked batch, as ordinary maths and untested by us. Say 200 g of sugar mixed with 50 g of carrier oil, so 250 g total.

Treating a millilitre as a gram slightly overstates the oil's weight if it is lighter than water, so the real percentage will be a little lower than shown, which errs toward under-dosing. Our own oil page says it dominates a blend quickly, so a start at 0.5% (about 25 drops in that batch, in a jar you will scoop from for weeks) is where reasoning from that sentence leads us. Mix the oil into the carrier first, then fold in the sugar so the drops are spread through the whole batch, not sitting in one pocket that lands on one patch of skin.

The bath, if you do want one

Reasoning from Tisserand's 5 to 20 drops range, a conservative start is the low end: 5 drops pre-mixed into an equal amount of polysorbate 20, stirred into a half ounce of a bath base you already use. How much a tub of water dilutes that is not the useful question, because a tub holding about 150 litres (our assumption) makes 5 drops (0.25 ml) look trivial on paper while the problem Tisserand describes is the surface film, not the average. Stir the water well before you get in and stay out if you see any oil slick. This is reasoning, not something we have run.

Two practical hazards that are ordinary common sense, not sourced findings: oil and carrier-oil residue make a tub floor slippery, and a scrub applied on a wet floor does too. Rinse the tub after, and use a mat.

One more rule that follows from Tisserand's film description: a scrub is not a bath additive. Do not tip a jar of oily scrub into a tub as a shortcut, since that recreates the floating film with the carrier oil and cilantro oil together. Use it in the shower or at the sink, and rinse off fully, away from eyes.

Skin-sensitivity facts that apply to a leave-on rub

Every fragrance oil can sensitise some people. A 2024 review in Cutis (Musicante, Cohen and Milam) lists fragrance among the common causes of contact dermatitis, in the armpit specifically, and says patch testing helps pin down the cause. For coriander, the only skin-tolerance trial we found, Casetti et al., Phytotherapy Research, 2012, put a cream and a lotion with 0.5% and 1.0% coriander oil on 40 healthy volunteers under an occlusive patch and observed no irritation. It was fruit (seed) oil, and the 2022 Kumar et al. analysis of leaf oils from four coriander cultivars found (E)-2-decenal, decanal, (E)-2-dodecenal and (E)-2-tetradecenal as the main components. Those are different chemistry from the seed oil Casetti tested, so applying that tolerance result to leaf oil is an inference, and a weak one. Hence the patch test. Our patch test guide covers how; our dilution article has the chart, which we will not repeat here.

Who should skip this

Skip a scrub on shaved, broken or inflamed skin and on the face. See a dermatologist before using any new scented product if you have eczema or a past reaction to fragrance. Ask a paediatrician or pharmacist before using essential oils in a child's bath, and your OB-GYN or midwife if you are pregnant. Not for internal use. We sell the one oil only, not salts, sugar, carrier oils or dispersants, so those come from a reputable cosmetic supplier. For soap, see our soap article and the craft uses list.

If you want to try it: our cilantro leaf oil, sold undiluted so every percentage above is yours to calculate, in the smallest size first, since the aroma divides people.

Cilantro Essential Oil bottle

Cilantro Essential Oil

Cilantro Essential Oil from our own shop, in sizes from 0.5 oz to bulk.

From $13.99

Shop Now →

Sources & Further Reading