Continuing Education Activity

Euphorbia tirucalli, commonly known as the pencil cactus or milk bush plant, is used extensively for ornamental purposes in the southern United States and contains a toxic sap to humans. In addition, the sap is among the most irritating plant substances known and causes harmful effects following dermal or mucous membrane contact, particularly ocular exposure. Thus, its timely identification and intervention help to reduce severe complications, including blindness. This activity reviews the evaluation and management of Euphorbia sap exposure and highlights the role of the healthcare team in improving care for patients with this condition.

Objectives:

• Review the toxicity in humans of Euphorbia tirucalli plants.
• Describe the typical history and physical findings following Euphorbia tirucalli sap exposure.
• Outline the evaluation and treatment of common Euphorbia tirucalli sap exposures.
• Identify and describe the treatment of severe complications related to Euphorbia tirucalli sap exposure.

Introduction

Euphorbiaceae is a large family of flowering plants found worldwide and encompasses over 8,000 species. Also known as the spurge family, it is divided into multiple genera. Plants belonging to the genus Euphorbia have been used in folk medicine to treat various conditions throughout ancient history.  Species such as Euphorbia tirucalli (pencil cactus), Euphorbia milii (crown of thorns), and Euphorbia pulcherrima (Poinsettia) are commonly used as decorative houseplants and in landscaping. Many Euphorbia species secrete a white, milky sap, called latex, that can cause harmful effects through dermal or mucous membrane contact, particularly ocular exposure.

Euphorbia tirucalli, also commonly referred to as the pencil cactus, milk bush, and firestick plant grows as a shrub or small tree without leaves, has succulent-like branches, and may grow up to 12 meters high. Euphorbia tirucalli produces an abundant amount of latex when pieces of the plant are broken or damaged. Although native to Africa, it is used extensively in the southern United States for ornamental purposes. Because of its proximity to humans, medical providers in regions where the plant is widespread must be aware of its toxicity. The Texas Poison Center Network reported 678 Euphorbia tirucalli exposures from 2000 to 2018, but it is likely that many exposures likely go unreported.[1] Euphorbia myrsinites, Euphorbia marginata, Euphorbia peplus, and Euphorbia trigona also cause irritant effects after contact with their latex.[2]

Dermal contact generally causes mild, irritant contact dermatitis, whereas ocular exposure to Euphorbia latex is a medical emergency that may lead to blindness without proper treatment. Ingestion of the latex is rare and usually only causes mild symptoms related to irritation of the oral cavity, esophagus, and stomach.

Etiology

The toxicity of Euphorbia latex has not been fully elucidated, but it is believed to exert its poisonous effects through pH-mediated necrosis and pro-inflammatory, immune-mediated mechanisms.[2]

The latex contains alkaloids and has been described as caustic.[3] Dermal exposure causes irritant contact dermatitis that may present similarly to chemical burns. Ocular exposure to Euphorbia latex has been associated with elevated ocular pH and causes a chemical injury to the cornea and conjunctiva.[4][5]

Diterpenoid substances found in Euphorbia latex are believed to play a role in its cytotoxicity.[3] Ingenols, a type of diterpene ester, have been isolated from the latex of various Euphorbia species and demonstrate cytotoxic and pro-inflammatory effects. Ingenol mebutate, found in the latex of Euphorbia peplus, is a topical therapy approved by the U.S. Food and Drug Association (FDA) to treat actinic keratosis. It is believed to cause cytotoxicity through a dual mechanism of action involving rapid necrosis of lesions and neutrophil-mediated cellular effects.[6]

Epidemiology

The incidence of toxicity related to Euphorbia latex is unknown. The Texas Poison Center Network reported 678 Euphorbia tirucalli exposures from 2000 to 2018; of these, 55.6% were male, and 72.1% occurred in adults age 20 and over. The location of exposure was the individual's residence in 94.4%.[1] Anyone handling the plants without proper personal protective equipment (PPE) is at risk for injury. Gardeners, landscapers, florists, and nursery employees may be at high risk for exposure.

Contact with the toxic latex is most often accidental, and patients may be unaware of what the culprit plant or substance is when they present with symptoms. Young children may experience more dermatitis symptoms after skin contact compared with older children and adults.[2] Oral ingestion is rare and usually does not cause serious complications. Likely, many individuals with only minor symptoms after Euphorbia latex contact do not seek medical attention.

History and Physical

Symptoms may be immediate or delayed after contact with Euphorbia latex. They may vary in severity based on the exposure location and amount of sap with which they come into contact. For example, patients might provide a history of gardening or landscaping and may report a sap or liquid squirting into their eye.

Following dermal exposures, patients might not know what substance is causing their symptoms or that their symptoms are due to plant material. Therefore, patients should be questioned regarding any new exposures to plants, chemicals, cosmetics, detergents, pets, or medications. Phytodermatitis symptoms after skin contact include burning, pain, and pruritis. Severe pain and irritation may be present, but symptoms are usually mild. Dermatitis symptoms tend to have a delayed onset beginning 2 to 8 hours after exposure, and they may progressively increase in severity.[7]

Ocular symptoms begin immediately following contact with Euphorbia latex. The exposure may involve sap squirting or dripping directly into their eye or may occur if the sap is on their hands and they rub their eye. Symptoms include severe pain, burning, lacrimation, photophobia, and potentially loss of vision.[8]

Ingestion of Euphorbia latex may irritate the oral cavity, throat burning, abdominal pain, nausea, and vomiting.[1]

Physical exam of the skin may reveal localized erythema, tenderness, blisters, vesicles, purpura, plaques, hemorrhagic bullae, or ulceration.[2] Findings may resemble a partial thickness burn, and affected areas will likely be tender to touch. Phytodermatitis findings are likely to occur in areas directly contacting the plant, most often the hands or fingers.

Ocular exam findings may range from mild conjunctivitis to severe keratouveitis or even blindness. Physical exam of the eye, including visual acuity assessment, pH testing, intraocular pressure (IOP) measurement, and slit-lamp exam, should be performed when ocular symptoms are present.[8] Fluorescein staining will aid in the detection of corneal epithelial defects. Elevated ocular pH, eyelid edema, blepharospasm, conjunctival inflammation, chemosis, corneal ulceration, corneal edema, punctate corneal defects, anterior segment cells, and flare, hypopyon, and elevated IOP have all been reported after ocular exposure to Euphorbia latex.[4][9][10][11][12] Abnormalities on the fundal exam are not expected.

Evaluation

After a confirmed or suspected exposure to Euphorbia latex has occurred, the priority is decontamination to prevent further injury. Wash the skin thoroughly with soap and water. Remove contact lenses if present. Eyes should be irrigated copiously with water or saline for a minimum of 30 minutes.[13] If ocular pH is elevated, continue irrigation until pH normalizes to approximately 7.

Laboratory and imaging studies are not required for isolated dermal or ocular exposures and are unlikely to reveal significant abnormalities. In Euphorbia latex ingestion with systemic symptoms such as prolonged vomiting or severe abdominal pain, it may be prudent to obtain serum chemistries to evaluate electrolytes and thoracic or abdominal imaging to evaluate for concomitant abnormalities. These events are rare, and studies should be tailored to the clinical presentation based on provider judgment.

If there is a concern regarding intentional ingestion, then recommend screening for co-ingestions including acetaminophen and salicylates in addition to routine studies such as the electrocardiogram. If the type of plant ingested is unknown, consider screening for cardiac glycoside ingestion with a serum digoxin level, as many plants contain cardiac glycosides that will cross-react with the digoxin assay. The digoxin level should only be used qualitatively and not quantitatively in cases of cardiac glycoside-containing plant ingestions.

Contact poison control if there are questions regarding the diagnosis, management, or in the rare event of severe toxicity.

Treatment / Management

Treatment of symptoms related to Euphorbia latex exposure is mainly supportive; there is no known antidote to Euphorbia latex.

For dermal exposures, oral antihistamines and analgesics may be used for pruritis and pain, respectively. Over-the-counter acetaminophen or nonsteroidal anti-inflammatory drugs (NSAIDs) are likely adequate to control pain in most cases. Topical corticosteroids may ease local pruritis and inflammation; however, they also have the potential to delay healing.[2] There is no consensus on whether these should be used after Euphorbia latex exposure, although they remain a standard treatment for most causes of irritant contact dermatitis.

After ocular exposure, ensure the patient has undergone adequate irrigation of the involved eye(s) and that the ocular pH is approximately 7. The treatment of corneal epithelial defects, keratouveitis, elevated IOP, and other ocular findings are not specific to Euphorbia latex exposure. Topical anesthetics such as ophthalmic tetracaine drops may be used for analgesia during evaluation but are not recommended long term and generally should not be prescribed on an outpatient basis due to the risk of corneal complications with prolonged use.[14]

Artificial tears, oral NSAIDs, and acetaminophen may help provide pain relief for ocular symptoms. If a corneal epithelial defect is present, topical antibiotics are recommended to help prevent secondary bacterial infections. If the patient wears contact lenses, consider an antibiotic with Pseudomonas coverage such as ophthalmic ciprofloxacin or ofloxacin. Topical corticosteroids and cycloplegics may be indicated for cases of keratouveitis, and IOP-lowering medications may be used in cases of elevated IOP.[10] 

Some recommend treatment with topical corticosteroids if the patient presents within 24 hours of exposure; however, others have reported good outcomes without steroid application.[10][15][5] If a hypopyon is present or if a bacterial infection is suspected, topical corticosteroids should be avoided. If the patient is presenting to a primary care clinic, urgent care, or emergency room, it is recommended to obtain an ophthalmology consultation. If urgent ophthalmology consultation is not available, patients should be referred to an ophthalmologist for a close follow-up to ensure proper corneal healing and monitor for complications.

Euphorbia tirucalli ingestions usually only cause mild symptoms, and treatment is supportive.[1] Cold fluids, ice, or ice cream may alleviate irritated oral mucosa, and viscous lidocaine may be considered for more severe cases. It is uncertain whether activated charcoal will help neutralize or prevent absorption of Euphorbia sap. However, it may be reasonable to administer in high plant ingestion cases that present within 1 hour, as long as the patient is otherwise an appropriate candidate for activated charcoal administration.[16] 

Anything that may induce vomiting should be avoided as this may re-expose and further damage the esophageal mucosa to the toxic latex. Gastric lavage is unnecessary for minor ingestions and may not effectively remove large plant particles if present. In the rare event of significant volume ingestion of Euphorbia plant material or isolated latex, whole bowel irrigation can be considered to expedite removing the toxin.[16] Supportive treatment with antiemetics and proton-pump inhibitors (PPIs) is appropriate for mild to moderate gastroenteritis symptoms.

Differential Diagnosis

Unless the patient provides a clear history of plant exposure, the diagnosis may prove elusive. When skin findings are present, the medical provider should consider a differential diagnosis for irritant contact dermatitis (ICD) from well-known sources, including acids, bases, solvents, cosmetics, and metals, in addition to plants. Allergic contact dermatitis, atopic dermatitis, cutaneous drug eruptions, and infectious etiologies should also be considered. Dermatophyte infections including tinea corporis and tinea manuum may mimic ICD findings. Scabies commonly affects the intertriginous areas on the hands and causes intense pruritis, although careful history and inspection will likely distinguish scabies from the phytodermatitis caused by Euphorbia latex.

Many plants outside of the Euphorbiaceae family are known to cause irritant contact dermatitis. The stinging nettle (Urtica dioica) causes an urticaria-like reaction after contact with its tiny, stinging hairs that contain irritating chemicals. Common household plants such as Philodendron and Dieffenbachia contain calcium oxalate crystals, as do some flower bulbs, including tulips, hyacinths, and daffodils.[17]

Calcium oxalate crystals cause local irritation and edema when contacted, mainly when moist surface, such as the oral mucosa. Poison ivy, poison oak, and poison sumac (Toxicodendron spp.) cause allergic contact dermatitis that presents as a classic, delayed type IV hypersensitivity reaction. Plants containing furocoumarins, including citrus plants, celery, parsley, and parsnips, cause phytophotodermatitis that may appear similar to other dermatoses. Skin findings isolated to sun-exposed surfaces may suggest a photosensitivity reaction.[18]

Given that ocular symptoms start immediately after contact with the Euphorbia latex, the medical provider will often narrow down the etiology to a plant substance. The differential diagnosis includes chemical exposure from acids, bases, solvents, or other cytotoxic agents, but fortunately, the treatment remains essentially the same regardless of substance.

Prognosis

The overall prognosis related to Euphorbia tirucalli sap exposure is excellent. Dermatitis symptoms may initially worsen over the first several hours after exposure but typically resolve within 3 to 4 days.[7] The degree of ocular toxicity is affected by the amount and duration of latex exposure to the eye. Following ocular exposure, pain and visual acuity may worsen over the first 1 to 2 days despite timely and copious irrigation.[8]

Corneal epithelial defects typically heal within 4 to 7 days but may require up to 10 days in some cases.[15] With prompt treatment, most patients will have complete resolution of signs and symptoms within 1 to 2 weeks, including, notably, return of visual acuity to their baseline.

Complications

Complications after exposure to Euphorbia latex are uncommon, but severe outcomes including blindness have been reported. Complications are uncommon following dermal exposure, but the affected areas are at risk for secondary bacterial infection. Patients with corneal epithelial defects are at increased risk for developing bacterial infections of the eye. Without treatment, corneal scarring, anterior staphyloma, corneal neovascularization, and blindness may result.[8][19]

Deterrence and Patient Education

When Euphorbia latex exposure has been confirmed, patients should be educated on the toxic nature of the plant and advised to avoid contact with similar plants if feasible. If the individual is required to handle these plants, they should be instructed to avoid direct skin contact and use PPE, including gloves and goggles. Gloves or clothing that come into contact with the plant or sap should be washed immediately. Ornamental Euphorbia plants should be kept out of reach of small children and pets. If the patient is at risk for future exposure to toxic plants, they should be encouraged to take photographs of plants and bring these to any medical evaluations for review.

Enhancing Healthcare Team Outcomes

Euphorbia tirucalli and certain other Euphorbia species contain a white latex that is among the most irritating plant substances described. Exposure to the sap can cause severe consequences in humans, most significantly following ocular contact, leading to blindness if left untreated. Due to their widespread proximity to humans worldwide, healthcare providers must recognize the risk associated with these plants and their toxic latex, particularly those working in acute settings such as primary care, urgent care, and emergency rooms. Early treatment is crucial in preventing adverse outcomes, including secondary bacterial infection and blindness.