What are calendula's therapeutic uses?

Overview

Calendula, well known as one of the ornamental marigolds, blooms month after month from early spring to first frost. Because calend means “month” in Latin, the plant’s lengthy flowering season is believed to have given calendula its name. The herb has been used to heal wounds and treat inflamed skin since ancient times.

An active ingredient that might be responsible for calendula’s traditional medicinal properties has not been discovered. One theory suggests that volatile oils in the plant act synergistically with other constituents called xanthophylls.

Therapeutic Dosages

Calendula cream is generally applied two or three times daily to the affected area. For oral use as a mouthwash, pour boiling water over 1 to 2 teaspoons of calendula flowers and allow to steep for ten to fifteen minutes.

Therapeutic Uses

Experiments on rats and other animals suggest that calendula cream exerts
wound-healing and anti-inflammatory effects, but double-blind, placebo-controlled
studies have not yet been reported. The best study on calendula so far was a
controlled trial comparing calendula to the standard treatment trolamine for the
prevention of skin irritation caused by radiation therapy. The researchers used
trolamine for comparison not because it has been proven effective but more as a
kind of acceptable placebo (trolamine is not thought to do much, even though it is
widely used). The study found calendula more effective than trolamine. However,
because this was not a double-blind study, the results mean little; mere
expectation of benefit is likely to cause patients and experimenters to perceive
benefit.

Creams made with calendula flower are a nearly ubiquitous item in the German
medicine chest, used for everything from children’s scrapes to eczema,
burns, and poorly healing wounds. These same German products are widely available
in the United States as well.

Calendula cream is also used to soothe hemorrhoids
and varicose
veins, and the tea reportedly reduces the discomfort of
canker sores. However, as yet there is no scientific evidence for any of these
uses.

Safety Issues

Calendula is generally regarded as safe. Neither calendula cream nor calendula
taken internally has been associated with any adverse effects other than
occasional allergic reactions, and animal studies have found no significant toxic
effects. However, the same studies found that in high doses, calendula acts like a
sedative and also reduces blood pressure. For this reason, it
might not be safe to combine calendula with sedative or blood pressure
medications.

Important Interactions

In persons taking sedative drugs, calendula might increase the sedative effect.
Also, internal use of calendula might amplify the blood pressure-lowering effect
of medications to reduce blood pressure.

Bibliography

Pommier, P., et al. “Phase III Randomized Trial of Calendula officinalis Compared with Trolamine for the Prevention of Acute Dermatitis During Irradiation for Breast Cancer.” Journal of Clinical Oncology 22 (2004): 1447-1453.