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What is Burdock Toxicity?

Burdock, scientifically known as Arctium minus, can grow up to six feet high. This invasive weed produces large, heart-shaped, hairy leaves on hollow stems, as well as brown seed pods with distinctive sharp burs made to attach to animals in order to spread to new sites. Flowers are produced in clusters of pink, purple or white petals. Found in uncultivated fields, along roads and fence lines, shaded areas, waste areas, moist soils, and often near livestock, burdock is common all over North America and Eurasia.

Burdock is a biennial weed that is not toxic if eaten. The plant can be problematic for owners due to its burs, which are covered with stiff, hooked spines that can attach to manes and tails. For your horse, they can irritate his mouth if eaten, become attached to his eyelashes, causing trauma to his eyes, or cause a skin reaction as the burs come into contact with these areas. 

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Symptoms of Burdock Toxicity in Horses

Symptoms of burdock toxicity can be seen on any areas that have come into contact with the burs of the plant. Signs include:

  • Mouth, tongue and teeth irritation
  • Mouth ulcers
  • Excessive salivation
  • Drooling 
  • Frothy saliva
  • Eye trauma
  • Corneal inflammation
  • Eye discharge
  • Corneal erosion
  • Pupil contraction
  • Corneal ulcers
  • Light sensitivity
  • Closed eye
  • Skin itching
  • Skin burning, reddening, or rash

Causes of Burdock Toxicity in Horses

The cause of trauma or irritation from the burdock plant is due to the sharp, hooked burs on the seed pods of the plant. These hooked burs can attach themselves to your horse’s fur or eyelashes, causing skin or eye trauma as the burs then scratch the skin or delicate tissues of the eyes. A burdock sliver is often called a pappus. If the burs come into contact with your horse’s mouth by becoming attached to nearby fur or if accidentally eaten, they can cause trauma to mouth and tongue tissues. The resultant skin irritation may be caused by chemical agents inside the burs, perhaps lactones called sesquiterpenes.

Diagnosis of Burdock Toxicity in Horses

Diagnosis of burdock toxicity is through the symptoms presented by your horse, and the presence of the burs of the burdock plant. Burs may be seen attached to mane, tail, or other fur areas, or may be present in full or part in the mouth. 

Eye problems without the obvious presence of burs may be diagnosed after an eye exam, which may show bur parts in the eye. Bur slivers may be difficult to see, and a correct diagnosis may only occur after the eye symptoms fail to respond to treatments for other eye conditions. Extensive magnification may be used to detect such tiny slivers.

Treatment of Burdock Toxicity in Horses

Treatment of burdock toxicity begins with removing any burs from your horse, and his environment. Combs can aid manual bur removal from your horse’s mane and tail. 

Larger bur slivers in the eye can be flushed free or removed manually. Smaller ones can be removed using a fluorescent dye to stain the eye, along with a magnifying lens. After the sliver is removed, topical antibiotic ointments or ophthalmic atropine ointment may be used several times a day to reduce inflammation and possible infection. Oral pain relievers may also be prescribed.

For skin irritation, the affected areas are generally washed, then a topical chlorhexidine soak is applied. An astringent topical solution, such as aluminum acetate, may be used, or topical antimicrobial creams that are free of corticosteroids.

Recovery of Burdock Toxicity in Horses

Once the burs are removed, and treatment has commenced, recovery occurs within 3 days to 2 weeks, depending on the severity of the irritation. You may need to apply creams, ointments, or washes to calm inflammations and reduce infections. You may also need to administer medications given by your veterinarian. The most important aspect of recovery is keeping your horse from reinjuring those areas by further contact with burdock burs.

Even though most exposures to the burs of the burdock plant occur in the fall and winter months, the best times to control the growth of burdock on your property is during the summer months of June and July. Use spot herbicide treatments on individual plants to eradicate burdock from your property, or manually chop down plants before they can bloom and seed. Be sure to remove any burs from your horse’s fur when you find them, and monitor your pastures, trails, and fence lines for emerging burdocks that may cause future problems for your horse.