Benefits
Topical use during cancer radiotherapy (supportive care, not a consumer use)
A phase III RCT (n=254 breast cancer patients) compared calendula ointment vs trolamine (Biafine, the standard of care) applied to the irradiated skin after each session during postoperative breast radiation. Calendula significantly reduced grade >=2 acute dermatitis (41% vs 63%, p<0.001). Patients also had fewer interruptions in radiotherapy and reported significantly less radiation-induced pain. Important limits: trolamine is an active cream, not an inert placebo; the trial was only single-blind, and the paper notes calendula was harder to apply, so patients could tell which cream they had. A later randomised trial in 82 women found no difference against a standard sorbolene cream, so the evidence is inconsistent. This is supportive care given alongside cancer treatment under medical supervision.
Skin repair support, applied topically (one small trial)
One small trial on this page tested wound healing: 34 patients with venous leg ulcers, marigold ointment applied to the skin twice a day for 3 weeks versus saline dressings. Total ulcer area fell 41.7 percent with the ointment versus 14.5 percent with saline (p<0.05), and the authors call their own results preliminary. The longer list sometimes quoted for calendula (episiotomy, surgical wounds, diabetic foot ulcers, burns) is not backed by any reference here. Venous and diabetic ulcers are medical problems that need a clinician, and nothing here tested calendula taken by mouth.
Diaper rash: topical comparison trial in infants
A randomised trial in 66 infants under 3 years compared calendula ointment (n=34) with aloe vera cream (n=32), applied 3 times a day for 10 days. There was no placebo and no untreated arm, so the improvement seen in both groups cannot be separated from the settling that happens with ordinary diaper care. Severity fell in both groups, and the calendula group had fewer rash sites than the aloe group (p=0.001). No adverse effects were reported in either group. One small topical trial, so treat it as preliminary.
Anti-inflammatory and antimicrobial activity (laboratory and animal models)
Calendula contains triterpenoid faradiol monoesters, flavonoids and saponins. The often-quoted comparison with indomethacin comes from mouse ear swelling experiments, not from people, and no study cited here measured inflammation in humans. Modest antimicrobial activity against bacterial and fungal skin pathogens. Traditionally used on minor skin irritation. Eczema and other diagnosed skin diseases were not tested by anything cited here, and calendula should not be presented as a substitute for a prescribed steroid cream.
Mechanism of action
Faradiol triterpenoid anti-inflammatory effect
The triterpenoid esters (especially faradiol-3-monoesters: laurate, myristate, palmitate) are the main anti-inflammatory constituents. The reported potency similar to indomethacin comes from mouse ear swelling models, not from human skin, so it is a laboratory comparison only. Inhibit cyclooxygenase and lipoxygenase pathways. The acidic supernatant fraction containing carbon dioxide-extracted triterpenoids has strongest anti-inflammatory effect — water/ethanol extracts have lower activity.
Pro-angiogenic effect (wound healing)
Calendula stimulates angiogenesis and granulation tissue formation in wound healing models, promoting capillary growth into wound bed. Polysaccharide and triterpenoid fractions both contribute. These are animal and laboratory findings. The only human wound data cited here is one small venous ulcer study.
Antioxidant (carotenoid + flavonoid contribution)
Lutein, zeaxanthin, β-carotene (the yellow-orange color), and flavonoid glycosides provide combined antioxidant capacity. Reduces lipid peroxidation in inflamed skin. Less relevant for topical antioxidation than the direct anti-inflammatory effect, but contributes to overall therapeutic profile.
Antimicrobial activity (modest)
Calendula extracts inhibit Staphylococcus aureus, E. coli, Candida albicans, and several dermatophytes in vitro — modest activity, not comparable to dedicated antimicrobials. May contribute to wound healing benefit by reducing local infection risk but not primary mechanism.
Clinical trials
Phase III randomized controlled trial (Pommier P, Gomez F, Sunyach MP, D'Hombres A, Carrie C, J Clin Oncol 22(8):1447-1453, doi:10.1200/JCO.2004.07.063).
254 patients post-breast cancer surgery receiving postoperative radiation therapy at Centre Léon Bérard, France (-). Randomized to calendula ointment (Pommade au Calendula par Digestion, Boiron Ltd) n=126 or trolamine (Biafine, the institutional reference) n=128, applied to irradiated fields after each session.
The primary endpoint was met. Calendula reduced grade 2 or higher acute dermatitis: 41% versus 63% (p<0.001), a 22 percentage point absolute reduction. Note that trolamine is an active cream, not an inert placebo, and the trial was only single-blind; the paper says calendula was considered harder to apply, so participants could tell which arm they were in. Patients on calendula had fewer radiotherapy interruptions and reported significantly less radiation-induced pain. Conclusion: calendula ointment was superior to trolamine cream for preventing acute dermatitis during breast irradiation. Guideline panels, including MASCC, have not endorsed calendula for radiation dermatitis, and a later randomised trial found no benefit against a sorbolene cream.
Randomized double-blind controlled clinical trial (Schneider F, Danski MT, Vayego SA 2015, Rev Esc Enferm USP 49(2):221-228, doi:10.1590/S0080-623420150000200006).
51 patients with head and neck cancer, not breast cancer, receiving radiotherapy in Brazil: 24 given topical calendula and 27 given essential fatty acids. The comparator was an active oil, not a placebo. Published in a Brazilian nursing journal.
Grade 2 radiodermatitis was more common in the essential fatty acids group than in the calendula group (p=0.0120), and the calendula group was slower to develop grade 1 radiodermatitis (p=0.00402). Different cancer site and different comparator from the French trial, so this is supporting evidence, not a replication. Small, with an active comparator rather than a placebo, and again a product applied to the skin.
Randomized controlled trial (Siddiquee S, McGee MA, Vincent AD, Giles E, Clothier R, Carruthers S, Australas J Dermatol 62:e35-e40, doi:10.1111/ajd.13434).
82 women undergoing breast cancer radiotherapy were randomised (271 screened; the recruitment target of 178 was never reached, and 81 were analysed) to topical Calendula officinalis lotion (<5% v/v) vs Sorbolene standard of care (10% glycerine in cetomacrogol cream).
A null result, not a mixed one. Grade 2 or higher dermatitis occurred in 53% of the calendula group and 62% of the sorbolene group: odds ratio 0.87, 95% CI 0.36 to 2.09, P=0.92. The authors conclude that the trial showed no difference between calendula and standard of care. The trial was underpowered and says so, 82 randomised against a target of 178, so it cannot show calendula works and it cannot establish non-inferiority either. No trial on this page compared calendula with no treatment at all, so nothing here shows it beats leaving the skin alone.