Many herbal remedies and nutritional supplements can damage the eyes, including some alternative therapies that are used by people trying to correct eye problems, new research reports.

According to a review of reported cases and medical literature, commonly used supplements including chamomile, ginkgo biloba, licorice, vitamin A and echinacea can cause a myriad of eye problems.

Study author Dr. Frederick Fraunfelder explained that supplements become dangerous to the eyes when people take them in large doses. They can cause problems including severe conjunctivitis, eye irritation, retinal bleeding and temporary loss of vision, the study found.

“Tell your physician what you take, as these products interact with other drugs,” Fraunfelder advises. “Recognize even herbal products and nutritional supplements have adverse reactions.”

People who choose to take supplements that can damage eyes should schedule an eye exam before beginning the treatment, then visit an eye doctor every year to monitor their eyes, he told Reuters Health.

Fraunfelder, who is based at the Casey Eye Institute in Portland, Oregon, explained that most people are unaware of how damaging supplements can be to the eyes. “Most consumers assume because a product is naturally occurring it is safe,” he said.

As a result, about forty percent of people who use alternative therapies do not discuss them with their doctors.

To investigate which supplements can cause the most eye damage, Fraunfelder reviewed all eye-related case reports submitted to the World Health Organization, the U.S Food and Drug Administration and the National Registry of Drug-Induced Ocular Side Effects, which contains data from as far back as 1976. He also combed the medical literature for additional reports of eye problems caused by supplements.

Fraunfelder, who presented his findings in the American Journal of Ophthalmology, found 30 instances in which canthaxanthine, a carotenoid that produces an artificial suntan when taken orally, caused changes to users’ retinas, including crystal deposits.

The researcher uncovered seven cases in which people rinsed their eyes with chamomile tea to treat styes and irritation, and instead developed severe conjunctivitis.

Echinacea is widely touted as useful for treating the common cold and flu, but Fraunfelder found seven cases in which users developed irritation and conjunctivitis after using it topically.

The researcher also discovered five cases of temporary vision loss apparently caused by licorice consumption, and 71 cases of niacin causing eye problems.

Fraunfelder noted that vitamin A is a particularly big threat to the eyes at high doses, and ginkgo biloba, a blood thinner, can cause retinal bleeding when combined with other blood thinners.

Most people were using the supplements for reasons unrelated to their eyes, including arthritis, inflammation and digestive problems.

SOURCE: American Journal of Ophthalmology, October 2004.