Calendula

Calendula officinalis L. belongs to Asteraceae, the daisy family. Linnaeus published the name in Species Plantarum in 1753; IPNI records it as 187894-1. NCBI Taxonomy files it as taxon 41496 with the common name pot marigold. It is usually grown as a hardy annual: a branching plant with soft, slightly sticky, aromatic, simple oblong leaves and solitary flower heads in shades from pale yellow to deep orange. Each head is a disc of small tubular florets ringed by strap-shaped ray florets. The fruits are curved, ridged achenes that curl like hooks or rings, a quick field mark among daisy lookalikes. The heads open in daylight and close in the evening and in dull weather. Its wild origin is uncertain and probably Mediterranean; it has been a garden plant for so long that it is known chiefly from cultivation. Field marigold, C. arvensis, is a smaller wild relative, not the pharmacopeial plant.

Tagetes is the source of most “marigold” confusion. Tagetes erecta (African or Aztec marigold) is indigenous to Mexico and Guatemala; T. patula is the French marigold of bedding schemes. Both have pinnately divided, strongly scented leaves rather than calendula’s simple ones. Tagetes erecta is the garland flower grown on a huge scale in India and the commercial source of lutein: FAO/WHO’s food-additive committee (JECFA) writes its specification as lutein from Tagetes erecta, made from hexane extracts of the flowers. A lutein capsule that says marigold almost always means Tagetes. A calendula ointment means Calendula. Same family, different genus, different chemistry, and only Calendula has an EMA herbal monograph.

Which part counts matters. The European Pharmacopoeia defines Calendulae flos as whole or cut, dried, fully opened flowers detached from the receptacle, of the cultivated double-flowered varieties of Calendula officinalis, with at least 0.4% flavonoids calculated as hyperoside. Double-flowered cultivars carry many more ray florets, so in practice the drug is mostly the orange rays; EMA assessors repeatedly speak of preparations from ligulate or ray florets only. The Czech pharmaceutical codex keeps a separate article for whole flower heads with the calyx (Calendulae flos cum calyce). Single-flowered garden plants, whole heads, and leaf-and-stem preparations are therefore not the same herbal substance. That distinction is not pedantry: EMA discounts several clinical studies, including the best-known radiotherapy trial, because their products were made from leaves and stems as well as flowers.

Chemistry, from EMA’s assessment report: triterpene saponins at 2–10%, oleanolic acid glycosides with glucuronic acid; triterpene alcohols, with about 0.8% monols (α- and β-amyrin, lupeol, taraxasterol, ψ-taraxasterol) and about 4% diols, mostly as fatty-acid monoesters of faradiol and arnidiol. Faradiol-3-O-myristate (PubChem CID 11763698) and faradiol-3-O-palmitate are the principal anti-inflammatory esters; Hamburger and colleagues (Fitoterapia 2003) also purified the laurate. Carotenoids reach up to 4.7%, predominantly lutein and zeaxanthin. Flavonoids run 0.3–0.8%, glycosides of isorhamnetin and quercetin. Coumarins (scopoletin, umbelliferone, aesculetin), 0.2–0.3% volatile oil, and up to 15% water-soluble polysaccharides complete the profile. The “sesquiterpene lactone calendin” of older literature is not a genuine constituent; EMA identifies it as loliolide, a carotenoid breakdown product. Calendula flowers largely lack the sesquiterpene lactones that make arnica a stronger skin sensitizer.

The genus name comes from Latin kalendae, the first day of the Roman month, because the plant was said to be in flower at the start of almost every month. Officinalis marks a plant of the apothecary’s workroom. EMA’s assessors trace documented therapeutic use of calendula flowers and ointments back at least to Hildegard von Bingen in the twelfth century. The kitchen history is as long. Calendula was “poor man’s saffron,” used to color and flavor soups, rice, custards, butter, and cheese, and John Lindley wrote in 1838 that it was chiefly used to adulterate saffron. William Turner’s 1551 herbal recorded the flowers as a yellow hair dye and their fumes as a way to “bring down” the afterbirth, the kind of uterine lore that still shadows the plant’s pregnancy cautions.

Professional medicine formalized the skin and mouth uses. Germany’s Commission E published a Calendulae flos monograph on 13 March 1986: internal and topical use for inflammation of the oral and pharyngeal mucosa, and external use for wounds, including slow-healing wounds and leg ulcers. Its dose was 1–2 g of dried flowers infused in 150 ml of water, 2–4 ml of tincture in a quarter to half litre of water, or ointments equivalent to 2–5 g of flowers per 100 g. The British Herbal Pharmacopoeia of 1976 reached further, to enlarged lymph nodes, sebaceous cysts, and duodenal ulcer; those claims never acquired trial support. Popular herb books also repeat stories of marigold wound dressings on battlefields, including the American Civil War. This monograph could not trace the Civil War version to primary medical records, so treat it as lore.

The modern regulatory file is cautious. The HMPC adopted its first calendula monograph and an EU list entry in 2008, then a revised monograph on 27 March 2018, both on the traditional-use tier. During that revision the committee reviewed newer trials, including Brazilian studies of a standardized calendula extract in leg and pressure ulcers and the Swedish radiotherapy trial, and still judged the evidence insufficient for well-established use. A further call for scientific data ran in 2024. Homeopathy runs on a parallel track: the Cochrane review of homeopathic medicines for cancer-treatment side effects (Kassab and colleagues, 2009) counted the Pommier ointment, made by the homeopathic manufacturer Boiron, as a homeopathic medicine. In the United States calendula is sold as a cosmetic ingredient, a dietary supplement, and a homeopathic product, three regulatory categories with three different standards.

EMA does not require pharmacology for a traditional registration, and no mechanism is established in people. The laboratory story centers on triterpenoids. Della Loggia, Tubaro, Sosa, Becker, Saar, and Isaac (Planta Medica 1994) fractionated a supercritical CO2 extract of calendula flowers in the croton-oil mouse-ear edema model and found the triterpenoids were the main anti-inflammatory principles. The faradiol monoester mattered most because it is the most abundant. Free faradiol, which was not present in the extract, was the most active compound and matched indomethacin. The anti-inflammatory activity of different CO2 extracts tracked their faradiol monoester content, which the authors proposed as a quality-control marker. Zitterl-Eglseer and colleagues (Journal of Ethnopharmacology 1997) isolated faradiol-3-myristate and -palmitate, found similar dose-dependent anti-edema activity for both with no synergy, and again found free faradiol equal to an equimolar dose of indomethacin.

Those esters are fat-soluble waxes recovered with CO2. A watery infusion, an olive-oil macerate, a petroleum-jelly ointment, and a hydroalcoholic tincture are therefore not chemically interchangeable, and a mouse ear swelling after croton oil is not a human wound closing. Other threads are weaker still: flavonoid and carotenoid antioxidant activity, polysaccharides, and antimicrobial and cytotoxic effects in dishes (MSKCC’s summary). Animal wound studies, pooled by Givol and colleagues (Wound Repair and Regeneration 2019), point to faster resolution of the inflammatory phase and more granulation tissue. That is a plausible basis for traditional skin use, not proof that a given cream works.

The allergy biology runs the other way. Strong Compositae sensitizers such as arnica owe much of their reputation to sesquiterpene lactones. Calendula flowers contain little of them, which is the likeliest reason Paulsen’s review (Contact Dermatitis 2002) judged calendula only weakly sensitizing experimentally and found the human evidence anecdotal. Weak is not zero. Cross-reactivity with other daisy-family plants cannot be excluded, and EMA keeps the family-wide contraindication.

The EMA indications are short. Traditional use, on the basis of long-standing safe use rather than trial proof: symptomatic treatment of minor skin inflammation such as sunburn, an aid in healing minor wounds, and symptomatic treatment of minor inflammation in the mouth or throat as a rinse or gargle. Skin use is for age six and up; mouth and throat use is for age twelve and up; symptoms lasting more than a week, worsening, or signs of infection go to a clinician. There is no EMA indication for swallowing calendula. MSKCC’s patient summary lands in the same place: small cuts and burns, irritated or inflamed skin, with other uses unstudied, and food and tea amounts generally safe.

Radiation dermatitis is the headline trial area, and it is split. Pommier, Gomez, Sunyach, D’Hombres, Carrie, and Montbarbon (J Clin Oncol 2004) randomized 254 women after breast-cancer surgery to calendula ointment or trolamine (Biafine) on irradiated skin. Grade 2 or higher dermatitis fell from 63% to 41%, with less pain and fewer treatment interruptions; the ointment was harder to apply. EMA’s assessors note the product was 20% fresh aerial parts in petroleum jelly and declined to treat it as evidence for the flower drug. Sharp and colleagues (Eur J Oncol Nurs 2013) randomized 420 Swedish women (411 analyzed) to a calendula cream or an ordinary aqueous cream: severe reactions were 23% versus 19%, with no difference at any point. Kassab’s 2009 Cochrane review called the calendula data preliminary and in need of replication. Robijns and colleagues’ 2023 meta-analysis in Supportive Care in Cancer found no significant calendula effect on grade 2 or higher dermatitis. Beating trolamine is not the same as beating a plain moisturizer.

Other topical trials are small and mostly unblinded. Duran and colleagues (2005) treated 21 people with venous leg ulcers with a calendula ointment and 13 with saline dressings: ulcer area fell about 42% versus 15% in three weeks. Buzzi and colleagues (J Wound Care 2016) reported faster venous-ulcer healing with a standardized hydroglycolic extract in 38 treated versus 19 control patients; the abstract does not describe randomization, and the second author’s listed affiliation is Phytoplenus Bioativos, a Brazilian company, although the paper declares no conflict of interest. Givol’s 2019 systematic review found two positive venous-ulcer studies but no benefit in a diabetic-ulcer trial or a burn trial. Panahi and colleagues (2012) found fewer diaper-rash sites with calendula ointment than with aloe cream in 66 infants, with no placebo arm. De Angelis and colleagues (2022) reported less episiotomy pain with calendula ointment than standard care in 100 women. Encouraging, uneven, and not enough for EMA’s well-established tier.

Weaker or misattributed uses: calendula capsules for stomach ulcers, menstrual problems, or immunity have no meaningful human trial base. Cytotoxic and antitumor results are cell-culture and rodent findings. The often-cited ear-pain trial (Sarrell and colleagues, Archives of Pediatrics and Adolescent Medicine 2001, 103 children) used Otikon, olive-oil drops of garlic, mullein, calendula, and St John’s wort; a four-herb blend that matched anesthetic drops says nothing about calendula alone. Eye-health lutein comes from Tagetes, not calendula. Homeopathic calendula pellets are a separate question from an ointment containing the plant.

The EMA monograph lists six herbal preparations: the dried, comminuted flower for infusion; liquid extracts 1:1 and 1:1.8–2.2 in 40–50% ethanol; a 1:5 tincture in 70–90% ethanol; a 1:10 extract in fatty vegetable oil such as olive oil; and a 1:5–1:25 extract in hardened vegetable fat or petroleum jelly. Skin posology: an infusion of 1–2 g of flowers in 150 ml of water, used still warm to soak dressings two to four times a day, with dressings removed after 30–60 minutes; the tincture diluted at least 1:3 with freshly boiled water for dressings; and semi-solid products containing the equivalent of roughly 2–20% flower depending on the extract type, applied as a thin layer two to four times a day.

Mouth and throat posology, for adolescents and adults: 1–2 g of flowers infused in 150 ml of water and used warm as a rinse or gargle two to four times a day, or the tincture as a 2% solution in water for gargling at the same frequency. The use is oromucosal; the rinse is spat out, not drunk as a treatment. Commission E’s older dosing was similar: 1–2 g per cup, 2–4 ml of tincture in a quarter to half litre of water, or 2–5 g of flowers per 100 g of ointment. If symptoms last longer than a week, EMA directs people to a doctor or qualified practitioner.

Shop products rarely say which of these they are. Infused oils, salves, creams, baby balms, and soaps often list calendula without a strength or plant part, and some are made from whole heads or aerial parts. Homeopathic labels are a separate category. A “mother tincture” cream contains the plant at material strength; EMA’s report describes a burn hydrogel with 10% homeopathic mother tincture. Pellets or creams labeled 6C or 30C are serial dilutions; beyond about 12C, it is unlikely a single molecule of the original extract remains. If you want the EMA object, look for Calendula officinalis flower, a stated extract type, and a stated percentage.

In the kitchen, fresh ray florets go into salads and dried petals color soups, rice, and butter; MSKCC regards food and tea amounts as generally safe. Those are culinary quantities, not the EMA wound protocol. Tagetes petals are not a substitute for calendula in a skin preparation, and garden flowers sprayed with pesticides belong in neither a salad nor a salve. Home-made oils are fine for intact, mildly irritated skin in people without daisy allergy; they are not dressings for deep, infected, or burned tissue.