Calendula: the salve herb worth using, assessed on what it actually delivers
Calendula infused oil at 10 to 30 percent, CO2 extract at 0.5 to 5 percent, faradiol ester content, drying and mould risk, plus the Asteraceae allergy caution.
Calendula is the one salve herb that survives scrutiny. It has an identified lipophilic active, a pharmacopoeial monograph, a European regulatory position and a low irritation record, which is more than can be said for most of the botanicals that end up in a tin. What it does not have is a strength you can assume. This page works out how much of the marker compound an infused oil at 20 percent actually carries, and what that entitles you to say.
Use dried flowers infused at 1 part herb to 5 parts oil by weight, and put that oil in at 10 to 30 percent of the formula, or use the whole oil phase. A CO2 total extract does the same job at 0.5 to 5 percent and is roughly an order of magnitude more concentrated. The marker compounds are faradiol monoesters, and nothing on the market is standardised to them.
Which part you are actually buying
Calendula officinalis L. is an annual of the Asteraceae, grown as pot marigold and not to be confused with the Tagetes marigolds, which are a different genus with a different chemistry and a much stronger odour. Two forms of the dried flower are sold, and the difference between them is the single largest variable in the whole subject.
- Whole flower heads (Calendulae flos in the pharmacopoeial sense) include the green receptacle, the bracts and the central disc florets as well as the coloured ray florets. Cheaper per kilogram, bulkier, and diluted by a lot of green material that contributes chlorophyll rather than triterpenoids.
- Ligulate florets, sold as petals, are the orange or yellow ray florets stripped from the head. Several times more expensive by weight, and richer in both the carotenoid colour and the triterpenoid esters that matter.
Published analyses consistently put the triterpenoid ester content higher in the ray florets than in the whole head, commonly by a factor of two to four. Buying petals therefore costs more per kilogram but not necessarily more per unit of active, and it makes a visibly better oil. Whole heads are the sensible choice when you are growing your own and the labour of stripping petals is the binding constraint.
Faradiol monoesters, the marker that matters
The lipophilic activity of calendula flowers tracks a small group of triterpendiol esters: faradiol 3-O-myristate, faradiol 3-O-palmitate and faradiol 3-O-laurate, collectively the faradiol monoesters. Work published in the 1990s fractionated calendula flower extracts against the croton oil mouse ear oedema assay and located the anti-oedematous activity in this fraction rather than in the flavonoids or the carotenoids, with the isolated monoesters performing comparably to indomethacin on an applied-dose basis. That is a mechanistic finding in an animal model, not a clinical result, and it should be treated as the reason to prefer an oil extraction over a water one, not as evidence that a balm does anything.
Three consequences follow directly.
- Fat is the right solvent. Faradiol esters are lipophilic. An oil macerate takes them up; a water infusion or a hydrosol does not. The general rule about what does and does not transfer is in herbal infused oils.
- Colour is not strength. The orange comes from carotenoids, principally lutein and zeaxanthin esters with some beta-carotene and flavoxanthin. Faradiol esters are colourless. A pale oil can be perfectly good and a vivid one can be weak, or dyed.
- Nobody sells to a faradiol specification. There is no pharmacopoeial assay for it and suppliers do not test for it. You are buying on cultivar, part, harvest and appearance, which is why batch variation is large.
What the monograph actually specifies
The European Pharmacopoeia monograph for calendula flower sets a minimum content of 0.4 percent flavonoids, expressed as hyperoside on the dried drug. That is a genuine identity and quality control, and it is worth asking your supplier whether the material meets it. But read what it is: an assay for the water-soluble flavonoid fraction, which is largely the part an oil infusion leaves behind. A batch can pass the monograph and still be poor in the constituents you are extracting.
This mismatch, between the assay that exists and the constituent you want, is the honest reason calendula sourcing is done by eye. Buy deep orange petals with intact colour and a fresh, slightly resinous smell, from a supplier who states the harvest year. Faded, brown-flecked or dusty material has been stored badly and both fractions will have suffered.
Drying, and the mould problem
Calendula heads are sticky and resinous at the base, and they hold water long after the petals feel crisp. That makes them one of the more deceptive botanicals to dry, and the reason calendula turns up disproportionately in mouldy salve stories.
Target below 10 percent residual moisture. Fresh heads are roughly 80 to 85 percent water, so 100 g of fresh flowers should yield about 15 to 20 g dried; weighing a known sample down to constant weight is the only check that is not guesswork. In a dehydrator at 35 to 40 C, loose petals take 2 to 4 hours and whole heads 8 to 12. Air drying on a mesh rack in a single layer takes 7 to 10 days in a warm, moving, dark airflow, and much longer packed deep in a basket, which is exactly how a batch goes mouldy on the rack before it ever reaches the oil.
The bench test: petals should shatter rather than fold, the receptacle should snap, and the material should not feel cool to the back of the hand. Cool means evaporation, and evaporation means water.
Do not infuse fresh calendula for a shelf-stable product. Water sealed under oil in an oxygen-poor pocket is the condition that makes herb-in-oil preparations hazardous, and the flower's own moisture is more than enough. Dried material is the whole safety margin here, and drying removes the conditions for growth, not the spores. If a finished batch develops a bloom or a musty note, the diagnosis is in mould in balm and the batch goes in the bin.
Infused oil: ratio and level
Work by weight, never by volume: dried calendula petals are so light that a cup of them weighs a fraction of a cup of chopped root, and volume recipes are how salve strengths become meaningless.
| Preparation | Herb to oil | Level in formula | Notes |
|---|---|---|---|
| Infused oil, standard | 1:5 by weight | 10-30% | The default. Deep orange, obvious in a pale balm |
| Infused oil, strong or double | 1:4, or 1:5 twice | 10-25% | A second charge of herb beats a longer steep on one charge |
| Infused oil, light | 1:8 | up to 100% of oil phase | Sensible when the infusion is the entire carrier and cost matters |
| CO2 total extract | n/a | 0.5-5% | Thick, dark orange, semi-solid. Melt into the oil phase below 60 C |
| Ethanolic tincture | 1:5 in ethanol | not usable | The solvent will not stay in an anhydrous balm. Do not add it |
For 200 g of finished oil, start with 40 g of dried petals and 250 g of a stable carrier, allowing for the 15 to 25 percent that stays in the spent herb. High oleic sunflower and olive oil both survive a warm infusion; grapeseed and hemp do not, and the ranking is in carrier oils compared. Add mixed tocopherols at 0.1 to 0.5 percent of the oil at straining, for the reasons in vitamin E and antioxidants. The infusion calculator will size a charge for a target finished weight, and a full worked salve with temperatures and a wax level is in calendula salve.
CO2 extract: a different order of concentration
Supercritical carbon dioxide extraction of calendula flowers yields roughly 2 to 5 percent of the dry weight of the herb as a thick, dark orange, semi-solid total extract. That means one gram of extract represents 20 to 50 g of flower, and because the process is selective for lipophilic material, the triterpenoid esters concentrate into it rather than being left behind. Suppliers who publish a figure usually give total triterpenoid esters in the low single-digit percent range for a total extract.
Set that against an infusion. In a 1:5 macerate, the lipophilic content of one part of herb is diluted into five parts of oil, and only some of it transfers. The extract is therefore something like fifty to a hundred times more concentrated per gram than the infused oil, which is why the use levels differ by that much. It also explains the practical rule: 0.5 to 1 percent CO2 total extract is broadly equivalent to using a 1:5 infused oil at 20 to 30 percent, and stacking both is how people end up with a balm that smells of hay and stains everything it touches.
The extract is not a drop-in replacement in every respect. It contributes almost no oil volume, so replacing infused oil with extract removes a chunk of your liquid phase and stiffens the balm; make the difference up with plain carrier. It carries a strong herbaceous, slightly resinous odour that a 20 percent infusion does not. And it costs a great deal more per kilogram, though not necessarily per finished tin, which is the comparison worth running.
How strong is a 20 percent infused oil, really
This is the calculation nobody publishes, so here it is with every assumption on the table. Treat the output as an order of magnitude, not a measurement.
| Stage | Faradiol monoesters | Assumption used |
|---|---|---|
| Dried ligulate florets | 0.2-0.5% | Literature band for petals; whole heads roughly a third to a half of this, with several-fold cultivar variation |
| 1:5 infused oil | 0.02-0.05% | One part herb into five parts oil, with about half the lipophilic fraction transferring |
| Balm at 20% infused oil | 0.004-0.010% | Straight dilution. That is 40 to 100 parts per million |
| Balm at 1% CO2 total extract | 0.02-0.08% | Extract at 2 to 8 percent triterpenoid esters, diluted 100-fold |
Forty to a hundred parts per million is a real quantity of a real compound, and it is also very little. It sits several orders of magnitude below the concentrations at which isolated faradiol esters were assayed, and well below what a registered herbal ointment delivers. The correct reading is that a 20 percent calendula infusion is a mild, traditional, pleasant ingredient with a plausible mechanism behind it, and that anyone promising more than that is selling something the arithmetic does not support.
If you want a genuinely stronger product rather than a stronger colour, the levers in order of effect are: use ray florets instead of whole heads, do a double infusion on the same oil, then add 0.5 to 1 percent CO2 total extract. Extending a single infusion from four weeks to twelve is the one thing that does not help, because the oil approaches saturation early and only oxidises after that.
Colour: transfer, staining and fading
A 1:5 calendula infusion is a strong orange-yellow, and at 20 to 30 percent of a formula it will dominate the appearance of any pale balm. That is usually the intention, but three things follow that catch people out.
First, it shifts every tint you add on top of it. A nude or pink lip balm built over calendula oil reads warmer and more orange than the same pigment load over plain sunflower oil, so match shades in the actual base, as covered in colourants and tints. Second, the carotenoids are photo-oxidisable and they bleach. In a clear jar on a bright shelf, an orange balm can visibly pale within weeks, and customers read that as the product going off. The mechanism and the packaging response are in tinted balm colour fading, and the storage advice you can reasonably give a buyer is in storing balms at home.
Third, and most usefully, fading does not mean the balm has lost its calendula content. Faradiol esters are colourless and considerably more stable to light than the carotenoids in front of them, so a balm that has gone from apricot to cream has lost its pigment and kept most of its triterpenoids. Whether it has also gone rancid is a separate question with a separate test, which is smell, not colour: see rancidity and oxidation.
Asteraceae allergy and what goes on the label
Calendula is a Compositae, and the family's characteristic contact allergens are sesquiterpene lactones. People sensitised to one member frequently react to others, so a calendula balm is a real risk for someone who reacts to ragweed, chamomile, arnica, feverfew, chrysanthemum, tansy or yarrow. Patch test clinics screen for this with a Compositae mix rather than with single plants, precisely because the cross-reaction pattern is the clinically useful unit.
Calendula itself is a comparatively weak sensitiser within the family, well below arnica, and safety reviews have found it acceptable for cosmetic use at the concentrations reported. The related salve herbs and their sharper restrictions are set out in arnica, comfrey and salve herbs.
The labelling implication is the part makers miss. Botanical extracts carry no mandatory allergen declaration in the EU or UK. The 26 named fragrance allergens, becoming a much longer list under the current revision, must be declared when they exceed the thresholds described in fragrance allergen labelling, but Calendula Officinalis Flower Extract simply appears in the ingredient list like any other name. A Compositae-allergic customer has no warning beyond recognising the word. If you sell into the sensitive-skin market, put the family in plain language on the pack, and point people at how to patch test a balm. It costs nothing and it is the difference between a returned tin and a complaint.
What you are allowed to say about it
The European Medicines Agency's committee on herbal medicinal products has adopted a European Union herbal monograph on Calendula officinalis L., flos, on the traditional use basis. Traditional use registration rests on a plant preparation having been in medicinal use for long enough that its safety is plausible and its effect acceptable, not on clinical trials. The monograph covers specified preparations for cutaneous use, in registered medicinal products, with defined strengths and directions.
None of that transfers to a cosmetic. Three points follow:
- The monograph applies to a medicine. A UK or EU product presented for treating inflammation or aiding wound healing is a medicinal product by presentation and falls outside Regulation (EC) No 1223/2009 entirely. Selling it as a cosmetic does not make it one, and the pre-market machinery you would then need is described in selling balms in the UK and EU.
- The monograph covers named preparations, not your macerate. A home 1:5 infusion in sunflower oil is not one of the specified extracts, and the monograph gives it no status at all.
- Cosmetic wording has to stay on the cosmetic side of the intended-use line. "With calendula infused oil", "for dry, rough-feeling skin", "comforting" are cosmetic. "Healing", "anti-inflammatory", "repairs damaged skin" and any reference to a named condition are not. The full claim-by-claim treatment is in cosmetic versus drug claims.
Two categories deserve a specific warning. Nappy rash products are regulated as skin protectant drugs in the United States and calendula is not a monograph active, which shapes what a nappy rash balm may say and who should be using one. And eczema is a diagnosed condition, so the evidence and the claim boundary are handled separately in balm for eczema evidence.
What to expect, honestly
The strongest clinical result associated with calendula is a randomised trial in patients undergoing breast irradiation, which reported less acute dermatitis with a calendula ointment than with the comparator. Subsequent trials in similar settings have been mixed, the preparations differ, and none of them used a home infused oil. Elsewhere the human evidence is thin, small and mostly on defined pharmaceutical preparations. Nothing in that body of work licenses a claim for a cosmetic balm, and a maker who cites it is citing a medicine's data for a product that is not that medicine.
So the case for calendula in a salve rests on narrower ground, and it holds up on that ground. It has an identified lipophilic constituent with a plausible mechanism, it extracts well into oil, it has a long record of low irritation outside the Compositae-allergic group, and it makes a distinctive, attractive product. That is enough reason to use it at 10 to 30 percent as the traditional base of a herbal salve.
The decision rule: use infused oil when you want the colour, the tradition and a low ingredient cost, and CO2 extract at 0.5 to 1 percent when you want the constituents without the volume or the fade. Use both only if you have decided the smell is acceptable. And whichever you choose, describe it as calendula, not as an active, because at 40 to 100 parts per million of the marker compound that is the only description the numbers will carry.
Frequently asked questions
How much calendula infused oil should I use in a balm?
Between 10 and 30 percent of the total formula gives an obviously calendula product with a strong orange colour. There is no upper safety limit that would stop you using it as the entire oil phase, and many traditional salves do exactly that. Below about 10 percent the colour and the character both become hard to detect.
What ratio of calendula to oil should I infuse at?
One part dried flowers to five parts oil by weight is the standard, with 1:4 for a strong macerate and 1:8 for a lighter one. Always weigh rather than measure by volume, because dried petals are extremely light and a cup of them varies enormously in mass. Expect to lose 15 to 25 percent of the oil to the spent flowers.
Is calendula CO2 extract better than infused oil?
It is more concentrated, not better. Supercritical extraction yields about 2 to 5 percent of the flower's dry weight as a lipophilic total extract, so 0.5 to 1 percent of it in a formula is broadly comparable to a 1:5 infused oil at 20 to 30 percent. The extract adds no oil volume, has a much stronger herbaceous smell, and costs considerably more per kilogram.
Can I use fresh calendula flowers for infused oil?
Not for anything you intend to keep. Fresh heads are 80 to 85 percent water, and water sealed under oil creates the low-oxygen, high-moisture pockets that make herb-in-oil preparations hazardous. Dry the flowers to below about 10 percent moisture first, which is 8 to 12 hours in a dehydrator at 35 to 40 C for whole heads, or 7 to 10 days on a rack.
Is calendula safe for people with allergies?
Not universally. Calendula belongs to the Asteraceae, and people sensitised to that family, including to ragweed, chamomile, arnica or chrysanthemum, may cross-react. Calendula is a weaker sensitiser than arnica and is generally well tolerated, but botanical extracts carry no mandatory allergen declaration, so state the family plainly on the pack if you sell to sensitive skin.
Why did my calendula balm lose its orange colour?
The colour comes from carotenoids, which photo-oxidise and bleach. In a clear jar in daylight a balm can visibly pale within weeks. This is a pigment change rather than spoilage, and the colourless triterpenoid esters are considerably more stable than the pigment. Judge whether a balm has gone off by smell, not by colour, and pack in opaque or tinted containers.
Can I say my calendula balm is healing or anti-inflammatory?
No. Those are medicinal claims. A product presented as treating inflammation or aiding wound healing is regulated as a medicine in the UK and EU and as a drug in the United States, regardless of what is in the jar. The European traditional herbal monograph for calendula flower applies to registered medicines and specified preparations, not to a cosmetic balm made with an infused oil.
Sources and further reading
- European Medicines Agency, Committee on Herbal Medicinal Products, European Union herbal monograph and assessment report on Calendula officinalis L., flos, London and Amsterdam.
- European Directorate for the Quality of Medicines and HealthCare, European Pharmacopoeia monograph: Calendulae flos (calendula flower), Strasbourg.
- Della Loggia, R., Tubaro, A., Sosa, S., and others, on the role of triterpenoids in the topical anti-inflammatory activity of Calendula officinalis flowers, Planta Medica, volume 60, 1994.
- Zitterl-Eglseer, K., and others, on the anti-oedematous activity of the principal triterpendiol esters of marigold, Journal of Ethnopharmacology, volume 57, 1997.
- Pommier, P., and others, phase III randomised trial of Calendula officinalis compared with trolamine for the prevention of acute dermatitis during irradiation for breast cancer, Journal of Clinical Oncology, volume 22, 2004.
- Cosmetic Ingredient Review, Safety assessment of Calendula officinalis-derived ingredients as used in cosmetics, Washington DC.
- European Parliament and Council, Regulation (EC) No 1223/2009 on cosmetic products, Article 2 and Article 20 on the scope of a cosmetic product and on claims.
Reviewed and updated 6 September 2026. Spotted an error? Tell us and we will fix and log it.