DOES IT WORK?BACKGROUND: Marigold flowers are commonly grown in gardens for their vibrant colours. The name probably derives from "Mary's gold" as the flowers were used in ceremonies to crown the Virgin Mary during May.
However, the term marigold is a good example of how confusing the naming of plants can sometimes be. The largest group of garden marigolds are various Tagetesspecies, also called African or American or French Marigolds. These are used as a source of food colorants and lutein, a food supplement with a role in healthy eyesight.
Another smaller group are the pot marigolds, which come from the Calendulagenus. One of these, Calendula officinalis, has yellow or orange flowers and has been used as a herbal remedy for many centuries. Although occasionally used orally, these flowers are usually used to make an oily extract, which is most commonly used in an ointment for the topical treatment of minor wounds, burns and skin problems. The dried flowers are sometimes added to herbal teas, but this is usually for their colour and appearance, not any specific effect.
Garden marigolds should not be confused with the marsh marigold or Mayflower ( Caltha palustris). This is a member of the buttercup family, while the Tagetesand Calendulaspecies are part of the daisy family. The marsh marigold is native to Ireland and was used in many Irish folk customs. Its use as a herbal remedy was very limited because it is a strong irritant. Marsh marigold should not be used orally or topically as it is likely to cause serious irritation.
EVIDENCE FROM STUDIES
In what follows, "marigold" refers only to Calendula officinalis. Much laboratory research has been conducted on these flowers and several active ingredients have been purified. These have been found to have anti-inflammatory and antimicrobial effects. In animal studies, experimental wounds were found to heal faster when treated with topical marigold ointment compared with placebo creams.
In spite of its long tradition of use, few studies have been published in humans. One study reported on 15 patients with burns and wounds that were not healing with conventional treatment. Many of the patients reported wound healing after using marigold ointment. Another study of people with burns reported better healing after marigold compared with pure Vaseline or a pharmaceutical ointment. These studies were not designed according to rigorous standards and gave few details on how the wounds were evaluated.
A well-designed trial was conducted in more than 250 patients receiving radiation therapy for breast cancer. Marigold ointment was compared with a non-steroidal cream for the prevention of radiation-induced skin problems. Those using marigold had better results, but more people discontinued using the ointment because of difficulties applying it.
PROBLEMATIC ASPECTS
Marigold extract has been used in more than 200 cosmetic products without reports of adverse effects. The only problems associated with marigold ointment have been allergic reactions. Marigold should be applied first in a test spot by anyone with allergies to the daisy family. This includes ragweed, chrysanthemums, daisies and many other herbs. Conventional skin-patch tests are available for this group of plants.
RECOMMENDATIONS
Calendulaointment contains several ingredients shown in the laboratory to be beneficial for healing skin problems. While this is supported more by tradition than clinical studies, the ointment may be useful, especially when other treatments are not working or have side effects. The best evidence supports its use to prevent skin damage from radiation therapy, although further studies are needed to confirm all of these uses.
Dónal O’Mathúna has a PhD in pharmacy, researching herbal remedies, and an MA in bioethics, and is a senior lecturer in the School of Nursing, Dublin City University
