Gardeners Beware! Milkweed Toxicity
As gardeners, we are aware of skin irritations due to contact from plants such as, Poisonwood (Metopium toxiferum), and Manchineel (Hippomane mancinella), found right in our Florida Keys backyards. But, the eyes, the eyes! Corneal Endothelial Toxicity, a toxicity that affects the inner most layer of the cornea and can cause symptoms such as light sensitivity, blurred vision, and extreme pain, is possible when working with some of our well-known, favorite plants, such as Milkweed, Asclepias sp. A common trait of these plants, is a milky sap which contains latex.
Milkweed, Asclepias sp., is very popular in the landscape, since it’s the larval host plant for Monarch and Queen butterflies. Additionally, it serves as a nectar source for many pollinators. However, care must be taken when handling and propagating Milkweed.
The milky sap of Asclepias sp. contains a mix of cardenolides, pregnane glycosides, and other cardiac glycosides. The damage, which is relatively short-lived, consists of corneal abrasions, edema, loss of corneal transparency and folds in the cornea. Exposure to even small amounts of Milkweed sap, such as a swipe across a sweaty brow, can affect the eyes; however, symptoms aren’t instant, often not appearing till hours later, further confusing diagnosis. Symptoms will often decrease in severity within 24 to 48 hours, though ophthalmologist care and steroidal eye drops will advance the healing process and help avoid infection. Some other common plants that contain cardiac glycosides are Oleander (Nerium Oleander ) and Avocado (Persea americana).
Many plants with a milky sap are capable of causing toxicity. Plants in the genus Euphorbia, also have a poisonous milky sap with varying levels of different terpenes. Symptoms and damage are much the same as those exhibited with Milkweed, though the abrasions are more dot like than linear stripes. Common plants found here in the Keys are, Pencil Cactus, (Euphorbia tirucalli) and Crown-of-Thorns (Euphorbia milii). Members of the Araceae family, which includes favored plants such as Antuhrium, Caladium, Philodendron and Dieffinbachia sp., can also cause eye issues, due to the calcium oxalate found in the sap.
When handling Milkweed and other plants with milky sap, it’s important to avoid contact with your eyes. Wearing eye protection and gloves will reduce your exposure. Wash hands immediately following any contact with the sap. If you are experiencing symptoms described above after working with Milkweed, wash your eyes out thoroughly with water or a saline solution. Contact your eye doctor and inform him/her of your exposure.
For more information about Milkweed and seed collection: https://xerces.org/milkweed-faq
Written by Susie Reutling, Monroe County Master Gardener Volunteer