Stinging Nettle Poisoning in Dogs

The stinging nettle plant can grow well over 10 feet tall and is commonly found in uncultivated areas of moist soil such as pastures, wasteland, and alongside streams. Dogs, humans, and other animals who come into contact with the stinging nettle will experience unpleasant symptoms that can intensify with repeated exposure.

The leaves and stems of the stinging nettle are covered with trichomes, little hairs that contain histamines and other chemicals that can cause a reaction that may last for many hours. Canines who are exposed to the plant, especially in a repeated incident, can be poisoned by thousands of injections of acetylcholine which can seriously affect the peripheral nerves. Symptoms as serious as tremors and breathing difficulties may arise. Recorded instances of death due to this plant are few in number, but it is a possibility with a severe poisoning after ingestion. If your dog comes into contact with the stinging nettle and is displaying signs of pain and toxicity, a veterinary visit is warranted without delay.

The stinging nettle plant is in abundance in many regions of North America. This plant is covered in small stinging nettle hair cells that break easily on contact, injecting secretions that cause numbness, pain, and itching to humans and animals upon exposure.

Humans that have experienced the pain caused by a stinging nettle will remember that the discomfort will begin soon after contact with the plant. Such is the case also for our canine friends. Some of the most reported symptoms in dogs who have brushed against or ingested the stinging nettle are:

• Redness of the skin
• Swelling of the skin
• Hives
• Intense itching and burning
• Vomiting
• Drooling
• Diarrhea
• Pawing at the mouth
• Labored breathing
• Loss of coordination
• Dilated pupils
• Twitching muscles

There have been reports of exposure by inhalation as well, whereby dogs running through fields may breathe in large amounts of the stinging nettle, causing intense pain in the nasal passages along with intensified reactions to the substances contained within the plant.

Types

The stinging nettle is known scientifically as Urtica dioica L. , from the family Urticaceae. Other common names for the plant are:

• Tall nettle
• California nettle
• Slender nettle

• Within the stinging nettle are histamines, acetylcholine, and 5-hydroxytryptamine
• The plant can be found in ditches, orchards, on farmland, and beside streams
• The plant releases secretions that enter the skin as the hairs break upon contact
• The hair tips are angled and hollow, allowing for easy puncturing of the skin
• The nettle will release toxic substances to the nerves of the body, and histamines that cause swelling

If your pet has returned from an off leash walk and is displaying signs of stinging nettle poisoning, or you have witnessed him coming into contact with this pain-inflicting plant it is a good idea to make a visit to the veterinary clinic in order to provide your pet with relief and to avoid further health complications. Wash his fur and skin if he is stable.

If possible, transport a piece of the plant in a container or bag, being careful not to inflict the stinging nettle pain on your own skin. Having a sample of the plant for positive identification will enable the veterinary team to make a definitive diagnosis in a timely manner. 

Diagnosis of the stinging nettle plant will be based on the history of the event and the clinical symptoms; the veterinarian will examine your dog and verify that his vital signs (blood pressure and heart rate) are normal. The veterinarian will take a look at your pet’s skin, nose, mouth, and eyes for signs of redness due to stinging nettle exposure. There is no specific test for determining this type of poisoning, but if your pet is displaying severe signs such as loss of coordination, excessive vomiting, or dilated pupils the veterinarian may want to perform blood tests and urinalysis to rule out other types of toxicities, or to determine if an underlying disease process is exacerbating the symptoms normally seen with exposure to stinging nettle. 

Fortunately, most cases of stinging nettle poisoning result in dermatitis only. If this is the situation with your pet, a gentle washing of the skin, and sometimes a light scraping of the skin’s surface (in a dog’s case particularly the pads of the feet and areas of the body where fur cover is sparse) to remove any embedded plant hairs will be the first step of treatment. A topical medication may be applied to ease the redness and itching. When a dog is having a more intense reaction to the sting and pain, an injection of atropine sulfate to counteract the poisoning and nerve sensitivity may be given, along with an antihistamine to relieve inflammation and swelling that may have resulted from the nettle penetration.

If your pet chewed on the nettle, the veterinary team will rinse your dog’s mouth with cool water in an effort to remove some of the nettle hairs and to provide relief from the sting.

In the rare case of severe poisoning by stinging nettle that may involve excessive vomiting and diarrhea, dogs may need to be given intravenous fluids to bring electrolytes back to normal. Medication, if needed for pain relief, reversal of nerve irritation, or to stop nausea and vomiting, can also be given easily through intravenous therapy, which will help to calm an anxious pet.

The majority of incidences of stinging nettle poisoning will end on a positive note after a period of several hours at most. Studies have shown that the effects of the nettle can be felt for up to 12 hours. There has been recorded documentation of a group of hunting dogs who suffered repeated exposure to large amounts of inhalation and penetration of the skin perishing as a result of stinging nettle poisoning without treatment; however, death is not at all common.

Because the stinging nettle grows so prolifically in fields, ditches and open areas with moist soil, it is recommended that you avoid these areas when allowing your dog off leash. Walking your pet on leash in a safe, nettle free park may be the wisest decision in order to avoid a painful, potentially harsh, experience for your pet.