Mistletoe: The legend, the lore, the possible cure for dry eye?

“Don’t stand under the mistletoe with anyone else but me,” unless perhaps you are having dry eye symptoms.

The origins and use of mistletoe date back to ancient times. It is a hemiparasitic plant that grows in North America and Europe on the branches and trunks of pine, oak, birch, and apple trees. In Norse mythology, Balder, the god of the summer sun, is killed by his blind brother Hoor with a mistletoe arrow tip fashioned for him by Loki, the trickster god. In South Africa, a juice concocted from mistletoe berries is used as an adhesive to trap small birds in tree branches. The ancient Celts and Germans revered mistletoe that grew on oak trees, the early Europeans used it as a ceremonial plant, and the Greeks and other early cultures believed it had mystical powers.

In European folklore, mistletoe was considered capable of bestowing life and fertility, of providing protection against poison, and of having aphrodisiac properties. In Scandinavia, mistletoe was revered as a peace plant, under which enemies or even embattled spouses could declare a truce or kiss and make-up.

Notwithstanding this long and varied history, mistletoe is used today to decorate homes during Christmas, and historically, has come to represent romance, fertility, and vitality. Anyone standing under a ball of mistletoe cannot refuse a kiss.

Yet, this parasitic plant may have some medicinal properties as well. According to the National Cancer Institute, mistletoe is one of the most commonly used alternative therapies for cancer, and has been studied in combination with both chemotherapy and radiation therapy

Researchers in China may have found another medicinal use for this lowly plant. In a recent study, published in the International Journal of Ophthalmology, researchers demonstrated that in postmenopausal women, eye drops that consist of a combination of mistletoe and carboxymethyl cellulose may help mitigate the symptoms and signs of dry eye.

They randomized 60 postmenopausal women diagnosed with dry eye to mistletoe combined with carboxymethyl cellulose eye drops (n=30) and controls (n=30) treated with normal saline eye drops. Before treatment and at 1, 2, 4, and 8 weeks after, researchers assessed the Ocular Surface Disease Index (OSDI), tear film function, tear protein, and corneal morphology via confocal scanning microscopy. For safety reasons, they also assessed blood pressure, glutamic-pyruvic transaminase, glutamic oxaloacetic transaminase, urine creatinine, and blood urea nitrogen at 8 weeks after treatment.

At 2 months, researchers found that treatment with the mistletoe combination improved symptoms of the ocular surface, OSDI, tear protein, and tear film function, compared with only slight changes in the control group (P < 0.05). In addition, average levels of corneal epithelium basal cells and inflammatory cells significantly decreased in women treated with the mistletoe combination compared with the control group (3174 vs 4309 cells/mm²; and 38 vs 158 cells/mm², respectively).

Further, in the control group, the number of nerves significantly decreased compared with normal females. In the group treated with mistletoe, the number of nerves was only slightly reduced, compared with normal females.

So if you happen to see mistletoe this holiday season, remember that this lowly little parasitic sprig may offer more than an excuse to steal a kiss.