While eye drops are suspected as the poisoning agent in a South Carolina death, experts say the chemical used to get the red out of your eyes is safe when used correctly. Eye drops designed to treat redness are not intended to be consumed orally, which is how the medication has caused illness and even deaths.

Lana Clayton, 52, was arrested recently on suspicion of murder in the July 21 death of her husband, Stephen Clayton, 64. Authorities say Lana Clayton confessed to the slaying after an autopsy found poisonous amounts of the chemical tetrahydrozoline in her husband's body. She told investigators that she put eye drops in his drinking water from July 19 to 21.

The Active Ingredient in Redness-Relieving Eye Drops

Commonly used drops marketed to reduce redness in the eyes typically contain tetrahydrozoline, which was approved by the U.S. Food and Drug Administration (FDA) in 1954 and belongs to a family of drugs called imidazoles. The chemical is found in Visine, Murine Plus, Altazine, Clarine and some other over-the-counter eye drops, according to Drugs.com.

The FDA considers the risk for these products to be low as they are labeled for external use only and are clearly marked "keep out of reach of children."

Imidazoles, including tetrahydrozoline, were developed as decongestants and vasoconstrictors. Constricting blood vessels in your eyes is how they "get the red out." Tetrahydrozoline has been used before in real-life and fictional murder attempts.

Symptoms of Red-Eye Drop Misuse

Intentionally or accidentally drinking eye drops can lead to toxic blood levels. When used in the eyes as directed to reduce redness, these types of eye drops are not absorbed systemically in amounts that lead to toxicity.

When consumed orally, tetrahydrozoline passes quickly through the gastrointestinal tract, rapidly reaching the blood and the central nervous system.

Symptoms of an overdose of tetrahydrozoline include drowsiness, slow breathing or absence of breathing, slow heartbeat, hypothermia and possibly even coma.

Children are Most at Risk of Visine Poisining

The threat typically is not criminal but accidental through ingestion by children or pets. Children find the small bottles of odorless, clear solution intriguing and may consume the contents. A typical bottle of eye drops contains anywhere from 15 to 30 milliliters of solution.

"Size of the individual and the total dose are the most critical issues for causing harm, and so children are most at risk," said Wiley Chambers, MD, an ophthalmologist with the Center for Drug Evaluation and Research at the FDA. "In general, sleepiness or drowsiness are symptoms of concern if children — particularly those below the age of 6 — consume more than 1 milliliter in a day."

Clinical pharmacologist and president of PharmaLogic Development, Inc., Gary Novack, PhD, agrees. "Because of their small size, even a dose as low as 1 to 2 milliliters may be toxic to children, according to the FDA website."

Putting two drops in both eyes six times a day would only equal about one milliliter of fluid. So, if used as directed and protected from children, the standard use of eye drops is considered safe for the average person.

If Someone Drinks Eye Drops

However, if someone ingests tetrahydrozoline, there is cause for alarm. According to the material safety data sheet you should NOT induce vomiting and you should do the following:

"Examine the lips and mouth to ascertain whether the tissues are damaged, a possible indication that the toxic material was ingested; the absence of such signs, however, is not conclusive. Loosen tight clothing sucha as a collar, tie, belt or waistband. If the victim is not breathing, perform mouth-to-mouth resuscitation. Seek immediate medical attention."