The first thing most people ask about our shaving aftercare is why it's blue. The answer is one ingredient, blue tansy essential oil, and the colour isn't added. It comes from a compound that forms when the plant is distilled. If you're here because you just shaved and want to know what to put on afterwards, our guide to what to put on your bikini line after shaving covers the whole after-step.
This article stays on the ingredient itself. It covers where blue tansy comes from, why the oil turns blue, what researchers have actually measured, how it differs from a plant with a similar name, and who should be careful with it.
In this article
- What blue tansy is
- Why the oil is blue
- What research says about blue tansy and skin
- Blue tansy and common tansy are different plants
- Who should be careful with blue tansy
- Blue tansy in Après, and in Lips
- Frequently asked questions
What blue tansy is
Blue tansy is a flowering plant called Tanacetum annuum. A 2023 study of the plant describes it as a Mediterranean herb that grows wild in northwestern Morocco, Portugal, Spain and southern France, and notes it's also known as Moroccan blue chamomile. It belongs to the daisy family, the same large group as chamomile, yarrow and marigold.
The oil sold as blue tansy is an essential oil, which means it's steam distilled from the flowering parts of the plant. Like most essential oils, it's a mix of dozens of compounds. In the Moroccan sample that 2023 study tested, the largest share was camphor, at about 17%, followed by compounds such as alpha-pinene, bornyl acetate and limonene.
The mix changes from one harvest to the next. The same paper compares its results with earlier studies of the plant, and the share of the blue compound ranged from about 3.5% in its own sample to nearly 18% in another. Where the plant grows, when it's picked and how it's distilled all change what ends up in the bottle.
Why the oil is blue
The blue comes from a compound called chamazulene. The surprising part is that the living plant doesn't contain much of it. It forms during distillation.
A 2024 study on how chamazulene breaks down explains the process: chamazulene is formed by the thermal decomposition of colourless matricin during the steam distillation process. Matricin is a colourless compound in the flower. The heat and steam of distillation turn it into chamazulene, which is a deep blue to violet. The same paper notes that chamazulene is found in the oils of other plants too, including German chamomile and yarrow, which is why German chamomile oil is blue as well.
Why the colour can change
Chamazulene is sensitive to light. In that 2024 study, researchers exposed it to strong UVA light in the lab. After three hours the blue had turned green, and after six hours it had faded to yellow. Kept in the dark, even at 50°C for 50 days, the compound stayed stable.
Those were lab conditions, far harsher than a bathroom shelf. Still, a blue oil keeps its colour best away from direct sunlight, with the cap closed.
What research says about blue tansy and skin
This is where it's worth being careful, because a lot gets said about blue oils online. Most of the research on blue tansy and chamazulene was done in test tubes, on cells or on animals. Very little was done on people, and none of it tested a finished skin product like the ones you'd buy.
Here is what the studies we read actually looked at.
Chamazulene and oxidation. The 2024 paper reviews earlier work showing that chamazulene can slow oxidation in lab tests and has been used to protect human skin cells grown in a dish from damage caused by reactive oxygen molecules. That's a measured chemical property of the compound in a lab.
Chamazulene on mouse skin. A 2025 study put a 0.4% chamazulene solution on the skin of mice exposed to UVB light. The researchers reported that it lowered signs of inflammation and changed fat metabolism in the skin it was applied to, and they called it a promising topical agent. The chamazulene in that study came from a different plant, and the subjects were mice.
Blue tansy oil in the lab. The 2023 Moroccan study tested the whole oil against a fungus that attacks date palms. That tells you about plant disease, not about your skin.
| What was tested | Where | What it found | What it doesn't tell you |
|---|---|---|---|
| Chamazulene alone | Lab tests and skin cells in a dish | Slows oxidation; helped protect cells from oxidative damage | What a skin product with blue tansy does on a person |
| Chamazulene on skin | Mice exposed to UVB light | Fewer signs of inflammation where it was applied | Whether the same happens on human skin, or at the amount in a product |
| Whole blue tansy oil | Lab test against a plant fungus | Strong activity against that fungus | Anything about skin |
Chamazulene is a compound with measured properties in the lab, and the research on people hasn't caught up. When a product with blue tansy says it soothes or cools, that describes how the whole formula feels on skin. These studies weren't testing that.
Blue tansy and common tansy are different plants
People sometimes worry when they read that tansy is toxic. That warning is about a different plant.
Common tansy, Tanacetum vulgare, is a relative of blue tansy, and its essential oil often contains thujone. A 2023 study of common tansy oil notes that the thujone type of tansy oil has been found in 15 countries, and that thujone is considered a neurotoxicant, though opinions on that have recently differed.
Blue tansy, Tanacetum annuum, is a separate species with a different oil. In the Moroccan sample described above, the main compounds were camphor, alpha-pinene, bornyl acetate, limonene and chamazulene, and thujone wasn't among the main ones.
That's why the Latin name on a label matters. If a label just says "tansy", it's fair to ask which one. On ours, the ingredient is blue tansy essential oil.
Who should be careful with blue tansy
Blue tansy is a plant extract, and plant extracts can cause skin reactions in some people. Three groups should take extra care.
People allergic to plants in the daisy family. DermNet, the dermatology reference, explains that compositae allergy is a contact allergy to plants in this family, and its list of these plants includes tansy, yarrow and both kinds of chamomile. It also notes that extracts of these plants are used in skin products and cosmetics, and that people with this allergy should avoid creams and cosmetics that contain them. If chamomile products or marigolds have ever given you a rash, ask a pharmacist or doctor before trying a product with blue tansy.
People who react to camphor or strong essential oils. Blue tansy oil naturally contains camphor. A pure essential oil is far stronger than a formula that contains it, so never put undiluted blue tansy on your skin.
Anyone with broken or very irritated skin. Let it settle first. A cut, a raw patch or a rash that's spreading needs a look from a doctor or pharmacist before any new product goes on it.
Patch test before the first use
The simplest check at home is a patch test: the same small spot of inner forearm, morning and night, for five to ten days, watching for redness or itch along the way. If nothing appears, an allergy is unlikely. Our article on body care for reactive intimate skin explains why this area deserves the slower start.
Blue tansy in Après, and in Lips
Most people meet blue tansy in our range through Après, our shaving aftercare, and the colour gives it away: there are no dyes in it, so the blue comes from the tansy oil. It's a two-phase oil made in Montréal that cools and soothes skin after shaving and hydrates with no greasy residue.
Seven ingredients make up the list: yarrow hydrosol, peppermint hydrosol, grapeseed oil, blue tansy essential oil, vegetable glycerin, hyaluronic acid and potassium sorbate. The two hydrosols are plant waters from distillation, and the peppermint one is where the cool feeling comes from.
One thing to notice if you have a daisy-family allergy: Après contains both blue tansy and yarrow hydrosol, and both plants are on DermNet's list. That makes it a product to skip, or to check with someone first.
How to use it: shake the bottle so the two phases mix, then smooth a few drops over freshly shaved skin, dry or slightly damp. No rinse. It works on the face, the body and intimate areas, externally only. Keep it away from the eyes and mucous membranes, and patch test first.
Après is $32 CAD ($24 USD) for 1 oz (30 mL), and the ingredients and directions are on the Après page. If you'd like the before-step too, the shaving ritual pairs it with Base, our pre-shave oil, for $54 CAD ($40 USD).
Blue tansy is also one of the five essential oils in Lips, our vulva balm, alongside ho wood, geranium bourbon, peppermint and palmarosa. Together they make up about 1% of that formula. Our guide to vulva balm ingredients explains how to read a balm label.
If razor bumps are the problem, the change that helps most is usually in how you shave. Our article on razor bumps on the bikini line goes through it.
Frequently asked questions
Why is blue tansy oil blue?
Because of a compound called chamazulene. The flower contains a colourless compound, matricin, and the heat of steam distillation turns it into chamazulene, which is deep blue. German chamomile and yarrow oils turn blue the same way. The colour is natural, so a product coloured by blue tansy doesn't need a dye.
Is blue tansy oil safe for skin?
It's used in diluted skin products, but it can cause reactions in some people. Blue tansy belongs to the daisy family, and people with an allergy to that family may react to it. It also contains camphor. Never use the pure oil on skin, and patch test any product with it for five to ten days first.
Is blue tansy the same as tansy?
No. Blue tansy is Tanacetum annuum, a Mediterranean plant, and common tansy is Tanacetum vulgare, a different species whose oil often contains thujone, which is considered a neurotoxicant. The toxicity warnings you may read about tansy refer to common tansy. Check the Latin name or ask the brand which plant they use.
Is blue tansy the same as blue chamomile?
They're different plants that share the same blue compound. Blue tansy is sometimes called Moroccan blue chamomile, which adds to the confusion. German chamomile is another plant whose oil also turns blue from chamazulene during distillation. Both belong to the daisy family, so the same allergy caution applies to both.
Does blue tansy help with irritation?
The research doesn't show that on people yet. Chamazulene, the blue compound, slowed oxidation in lab tests and lowered signs of inflammation on mouse skin in one study. No study we found tested a blue tansy skin product on people. A product's job comes from its whole formula and what its label says.
Why does my blue oil look green?
Light can change it. In a lab study, strong UVA light turned chamazulene from blue to green within hours, then to yellow. Store blue oils with the cap closed, away from direct sun. If a product has changed colour a lot, write to the brand before you use it.
Sources
- What blue tansy is, where it grows, and its oil's composition: Ettakifi and colleagues, Antibiotics, 2023, PubMed 37760747
- How chamazulene forms during distillation, where it's found, and how light changes it: Gabbanini and colleagues, Molecules, 2024, PubMed 38893479
- Chamazulene applied to UVB-exposed mouse skin: Zhou and colleagues, Antioxidants, 2025, PubMed 41300477
- Common tansy oil and thujone: Karcheva-Bahchevanska and colleagues, Molecules, 2023, PubMed 37630407
- Contact allergy to daisy-family plants: DermNet, Compositae allergy
About this article
Written by the Peach & Cream team, based in Montréal. Published October 15, 2026. Last updated October 15, 2026. Product facts come from the Après and Lips product pages; research findings come from the studies listed above. This article is general information, not medical advice. Après does not treat or prevent any condition.