Is Your Garden a Poison Paradise?

Never mind the serpent, sometimes the fig leaf is the real danger in paradise.

When Olaf Krull set to work pruning a fig tree in his Woodland Hills garden he didn’t expect to end up in the emergency room with third degree burns. However, when the milky sap comes in contact with human skin it can cause something called phytophotodermatitis.

A case study published in the medical journal Burns in 2008 by researchers Mirren Ramniklal Mandalia, Richard Chalmers and Frederick Schreuder, describes how the sap, rich in “phototoxic agents,”  or “flurocoumarins,” can prevent human skin from blocking solar UV radiation, causing severe skin burns.

The substance helps certain plants defend against fungal infections. However, “on contact with skin, furocoumarins bind with DNA,” the study stated. “Exposure to UV light causes cross-linking of the DNA, which blocks cell division, DNA repair, DNA synthesis, and eventually causes cell death.”

The result? Painful, raised plaques on the epidermis, that behave like burns, creating large blisters. Healing can take weeks, and victims of this kind of burn may experience “hyper-pigmentation”—discolored patches that remain sensitive to sunlight for months, or even years.

Figs aren’t the only potential cause of this type of chemical burn. Citrus sap—anecdotal evidence suggests lime is the biggest culprit—and members of the carrot and parsley family, including parsnips, dill, and celery, can also potentially cause phytophotodermatitis. The sap and even sawdust from the California black walnut can also cause burn-like reactions in not only humans but also dogs.

Some perfumes may also trigger a similar effect, called “berloque dermatitis.” Skin allergy sufferers may want to avoid perfumes that contain lime or bergamot orange;  galbanum—another member of the carrot family that is used in perfume to give a “green” scent—and ambrette seed, a medicinal plant in the mallow family that is used in perfume for its sweet, musky fragrance.

The sap of many Euphorbias, a family of plants with many drought tolerant strikingly beautiful species that are increasingly popular as Southern California garden plants, can cause another type of dermatitis: painful rashes, facial swelling, temporary blindness, and in severe cases, anaphylaxis. Many euphorbias are also toxic if consumed by children or pets. Plants in this family include crown-of-thorns and Euphorbia tirucalli, better known as pencil cactus, or fire sticks. Both plants can cause severe eye irritation or even permanent blindness, but when E. tirucalli is cut or damaged, the milky white sap tends to spurt out, increasing the risk of eye injury.

The sap of Terracina spurge, a euphorbia that has escaped from gardens to run amok in the Santa Monica Mountains where it is a noxious weed, can cause a poison oak-like rash. The popular holiday plant Poinsettia also belongs to this family, but it is less toxic than previously thought. At worst, consuming this plant may give a child or pet an upset stomach.

One of the most common causes of fatal poisoning in pets is the sago palm or king sago. All parts of this palm-like plant are toxic—even the pollen, which reportedly can cause headaches and aggravate asthma, but the real danger is from its bright orange seeds, which is deadly to dogs, causing irreversible liver failure. Sago isn’t a “true” palm; it’s a member of the ancient cycad family, plants that were around when the dinosaurs roamed the earth. Sago is one of the leading causes of plant toxin mortality in dogs, according to numerous studies, but children have also been victims of cycad poisoning.

The best way to avoid accidental cycad poisoning is to remove the seed-bearing female cones and pollen-forming male cones before they ripen. Contact with the sharp ends of cycad fronds or the spines on the plant’s trunk can cause rashes and infections, so all parts of the plant should be handled with care.

The spines and sap of agaves, one of the most popular plants for drought-tolerant landscaping, can also cause severe rashes and infected wounds. Calcium oxalate raphides, sharp crystals of oxalic acid, are the defense mechanism in the sap that protects these plants from predators. A similar chemical can be found in the sap of the houseplant dieffenbachia.

The beautiful datura flower and its tropical cousin, the angel trumpet, also known as brugmansia, present another kind of toxicity. Both plants contain high levels of highly toxic tropane alkaloids—scopolamine, hyoscyamine, and atropine.

Datura, also known as Jimson weed, has been known to make unsuspecting gardeners ill just through skin contact, but teenagers seeking a mind-altering experience are the most common victims of datura poisoning. Children are the most common victims of brugmansia poisoning, because the flowers are tempting to handle or put in the mouth.

Oleander, prized for its colorful flowers and ability to thrive in almost any conditions, is also highly toxic. Accidental poisoning in humans and pets is reportedly rare because the leaves have a terrible taste. However, horses, goats and llamas are all at risk from this beautiful but deadly plant, and the sap can cause painful rashes and eye irritation. Smoke from burning the wood is also toxic. This is one plant that should never end up as firewood or in the compost pile.

Sensitivity to plant toxins varies greatly: some people break out in rashes handling common garden plants like tomatoes or melon vines, others are unaffected by even the most powerful skin irritants, like poison oak. The list of plants that can cause contact dermatitis is long, and includes everything from the blue-flowered plumbago bush, and silk oak tree, Grevilea robusta—which causes a skin and eye condition known as “Gravilea poisonin”— to the ubiquitous English ivy and Virginia creeper, both of which also have poisonous berries.

Planting potentially toxic plants in a place where children and pets won’t come in contact with them, and avoiding spiny or toxic plantings near pathways or high traffic areas are simple measures to avoid contact. Creating a fenced “safe play space” for pets and children is the best way to prevent problems involving ingesting toxic plant material.

California Poison Control (CPC) recommends that parents of young children take a good look at their garden and learn the names of the plants so Poison Control or medical personnel will know what they are dealing with in an emergency. According to CPCl, more than 100,000 exposures to toxic plants are reported to poison centers throughout the United States each year. Most exposures are of “minimal toxicity,” but serious medical complications, and sometimes even fatalities, occur.

Small children run the greatest risk of ingesting poisonous plants—eight out of ten incidents of plant toxicity involve children under six—but adults who work with plants are at highest risk of plant-related contact dermatitis. Wearing safety glasses, long sleeves, and gloves while trimming plants or weeding can prevent most plant-related problems for adults.

RESOURCES

• UC Davis offers a short but comprehensive list of plants that are toxic to animals: http://www.vetmed.ucdavis.edu/ccah/health_information/plants_pets.cfm.
• The ASPCA provides extensive plant toxicity information for pet owners: http://www.aspca.org
• Immediate medical treatment is recommended for all toxic plant related emergencies.
• Poison Control can be reached 24 hours a day at (800) 222-1222.