Native to southern Europe, calendula is now widespread throughout central and southern Europe, Western Asia, and the United States. This familiar garden flower has long been touted as a topical anti-infective remedy for wounds resistant to healing. Calendula is used as a therapy for a wide array of skin disorders ranging from chapped hands to lacerations.

According to the German Commission E, topical applications of calendula are safe and efficacious in decreasing inflammation and promoting granulation of wounds, burns, eczema, and other inflammatory skin conditions.

Calendula is also traditionally used to treat spasms, fever, suppressed menstruation, cancer, and a host of other ailments. Despite its varied folk medicinal uses, researchers have not been able to identify precise structure-activity relationships for the pharmacological properties of this plant.

Calendula is typically an annual that thrives in any soil. Its herbaceous, branching stems grow to a height of 30 to 60 cm. Its erect stem is angular, downy, and branched. A tap root averaging 20 cm in length gives off multiple, thin, secondary roots. The leaves are alternate and tomentose. Those near the ground are hairy with a spatulate base while higher-positioned leaves are smaller, with an oblong to lanceolate shape.

Calendula has a composite flowerhead situated on a well-defined green floral receptacle that crowns each stem. The inner portion of the flowerhead consists of orange-yellow, tubular florets. These ligulate florets, sometimes inappropriately called petals, are the medicinally most important part of the plant.

Flowers (dried flower head or dried ligulate flowers)

Flavonoids: flavonol (isorhamnetin, quercetin) glycosides including isoquercitrin, narcissin, neohesperidoside, rutin; terpenoids, including lupeol, longispinogenin, oleanolic acid, arnidiol, brein, calenduladiol, erythrodiol, faradiol, helantriols, maniladiol, ursadiol, oleanolic acid saponins, sterols; volatile oils containing terpenoid components; bitter substance; carotenoid pigments; polysaccharides; lutein (carotenoid).

Calendula products consist of tinctures, liquid extracts, infusions, ointments and creams. They are made from either the aerial parts or the flowers collected when the plant is flowering. The ray florets of the completely unfolded and dried capitula are used in medicinal preparations.

Raw plant material of other genera in Asteraceae such as arnica and saffron are sometimes adulterated with calendula. Calendula products should be always be protected from light and moisture, and never stored for more than three years.

External: oral and pharyngeal mucosa, wound healing, crural (leg-related) ulcers, enlarged and inflamed lymph glands, artheroma, acute and chronic skin inflammation, varicose veins, phlebitis, thrombophlebitis, dermatological conditions (wounds, furunculosis, or boils, dry dermatosis, acne, eczema, anal eczema), proctitis (rectal inflammation), conjunctivitis; also a constituent in topical preparations for dry skin, bee stings, and frostbite.

Internal: inflammatory conditions of internal organs, gastrointestinal ulcers, dysmenorrhea; liver disease, toothache, fatigued limbs, eye inflammation or degenerative eye conditions; also administered a diuretic, and diaphoretic during convulsions, fever, and obstipation (intractable constipation). 

Conditions: inflammation of oral and pharyngeal mucosa; crural ulcers, skin tissue healing.

Clinical applications: 

• Flower: internally for inflammation of the mouth and pharynx; externally for wounds and burns
• Herb: internally for circulatory disorders, ulcers, spasms, jaundice; externally for swelling of the hands, jaundice, wounds, eczema

Calendula flower extracts have numerous pharmacological properties, including antimicrobial, antiphlogistic (treatment for fever and inflammation), immunostimulant, antitumor, estrogenic, choleretic (stimulates hepatic production of bile), and hemolytic activity.

In an in vitro study, an organic extract of flowers from Calendula officinalis showed anti-HIV activity in a MTT/tetrazolium-based assay. The extract also induced a significant dose- and time-dependent decrease in HIV-1 reverse transcription activity. In other in vitro research, calendula extracts elicited an uterotonic effect in rabbit and guinea-pig preparations. Calendula also possesses trichomonacidal properties, presumably due to the terpenoid fraction of the essential oil. The volatile oil fraction has been associated with antispasmodic activity.

Calendula extracts had antitumor activity against mouse Ehrlich carcinoma both in vitro and in vivo. The saponin-rich fraction showed the greatest amount of cytotoxic activity in vivo, but not in vitro. Other research suggests that flavonoids and high molecular weight polysaccharide fractions are responsible for the immunostimulant action.

In an in vivo study, calendula extracts exhibited topical anti-inflammatory and wound-healing activity, primarily through a mechanism involving granulatory action. In rats, calendula produced a weak anti-inflammatory effect in carrageenan-induced edema in rats. Although the constituents responsible for wound healing have not been identified, wound-healing activity is associated with a hydroalcoholic extract of calendula herb. The tissue-healing effect has been attributed to a synergism between the volatile oil and xanthophylls in calendula.

An extract consisting of calendula and allantoin proved more efficacious than allantoin alone in promoting tissue regeneration and epithelialization of surgically induced skin wounds in rats. In other animal research, a botanical extract containing calendula was effective for burn-induced edemas and acute lymphedema. And in a clinical investigation, patients receiving a multi-plant proprietary cream containing calendula reported a decrease in post-mastectomy lymphedema-related pain. However, there were no significant clinical differences between the experimental and control groups in the reduction of edema.

In another experiment, mice were inoculated with WAZ-2T (-SA) mammary tumor cells and then given dietary lutein extracted from calendula. Very low quantities of dietary lutein (0.002%) were more effective than higher levels in reducing mammary tumor incidence, tumor growth, and lipid peroxidation as well as in prolonging tumor latency.

• Infusion: 1 tsp. dried florets in 8 oz. water; steep 30 to 40 minutes; drink two to three cups per day
• Fluid extract (1:1 in 40% alcohol): 0.5 to 1.0 ml tid
• Tincture (1:5 in 90% alcohol): 2 to 4 ml tid
• Ointment: 2 to 5 g crude drug in 100 g ointment

Calendula is generally free of adverse side effects. However, both the flower and herb have a low potential for sensitization through frequent skin contact. Cytotoxic effects have been observed in vitro for this plant.

Although no major warnings are reported, calendula is known to affect the menstrual cycle. It has produced uterotonic activity in vitro, presumably due to triterpenoid compounds which can act as abortive agents. In light of the limited data on toxicology, calendula should not be used, or used with caution, during pregnancy and lactation.

No clinically significant interactions between calendula and conventional medications are known to have been reported in the literature to date, including the German Commission E monograph (Blumenthal 1998).

Commission E approves calendula flower preparations for internal use, and for external treatment of crural ulcers and poorly healing wounds.

Blumenthal M, ed. The Complete German Commission E Monographs. Therapeutic Guide to Herbal Medicines. Boston: Integrative Medicine Communications; 1998: 100.

Boucard-Maitre Y, et al. Cytotoxic and antitumoral activity if calendula officinalis extracts. Pharmazie. 1988; 43:220.

Casley-Smith JR. The effect of "Unguentum lymphaticum" on acute experimental lymphedema and other high-protein edemas. Lymphology. 1983; 16:150-156.

Dorland's Illustrated Medical Dictionary. 25^th ed. Philadelphia: W.B. Saunders; 1974.

Fleischner AM. Plant extracts: To accelerate healing and reduce inflammation. Cosmet Toilet. 1985; 100:45.

Gracza L. Oxygen-containing terpene derivatives from Calendula officinalis. Planta Med. 1987; 53:227.

Grieve M. A Modern Herbal. Vol. I. New York: Dover; 1971: 517-518.

Gruenwald J, Brendler T, Christof J. PDR for Herbal Medicines. Montvale, NJ: Medical Economics Company; 1998: 704-706.

Isaac O. Die Ringelblume. Botanik, Chemie, Pharmakologie, Toxikologie, Pharmazie und therapeutische Verwendung. Wissenschaftliche Verlagsgesellschaft mbH, Stuggart; 1992.

Kalvatchev Z, Walder R, Garzaro D. Anti-HIV activity of extracts from Calendula officinalis flowers. Biomed Pharmacotherapy. 1997; 51(4):176-180.

Kioucke-Popova, et al. Influence of the physiological regeneration and epithelization using fractions isolated from Calendula officinalis. Acta Physiol Pharmacol Bulg. 1982; 8:83-87.

Newall C, Anderson L, Phillipson J. Herbal Medicines: A Guide for Health-care Professionals. London: Pharmaceutical Press; 1996: 58-59.

Park JS, Chew BP, Wong TS. Dietary lutein from marigold extract inhibits mammary tumor development in BALB/c mice. J Nutr. Oct 1998; 128(10):1650-1656.

Schulz V, Hansel R, Tyler V. Rational Phytotherapy: A Physician's Guide to Herbal Medicine. 3^rd ed. Berlin: Springer; 1998: 259.

Shipochliev T. Extracts from a group of medicinal plants enhancing the uterine tonus. Vet Med Nauki. 1981; 4: 94-98.

Thomson WA. Medicines from the Earth: A Guide to Healing Plants. Alfred Van Der Marck ed. Maidenhead, England: McGraw-Hill Book company (UK); 1978:61.

Tyler V. The Honest Herbal: A Sensible Guide to the Use of Herbs and Related Remedies. 3^rd ed. New York: Pharmaceutical Products Press; 1993: 75-76.

Wagner H, et al. Immunostimulating polysaccharides (heteroglycans) of higher plants. Arzneimittelforsch. 1985; 35:1069.