Oxalates (Insoluble) Poisoning in Dogs

Oxalates are a poisonous component that is common in a number of plants. Depending on the species, oxalates may be either insoluble or soluble. Soluble oxalates are associated with hypocalcemia, kidney failure, and other systemic problems. Insoluble oxalate crystals cause severe irritation and swelling in the oral cavity and gastrointestinal tract if ingested.

Many common houseplants like dumb cane, philodendron, peace lily, and others contain insoluble oxalate crystals. These needle-like crystals are large enough to be visible in damaged plant tissue when stems and leaves are broken. Insoluble oxalates are not broken down metabolically by the body, but they can cause skin irritation upon contact, and swelling in the mouth, pharynx, or esophagus when eaten. If enough are swallowed, they will produce gastrointestinal irritation. Plants with insoluble oxalate content are toxic for both humans and animals, but dogs that like to chew on houseplants are most at risk. The sharp crystals cause pain and irritation upon contact, so it’s rare for dogs to swallow enough plant material to produce serious damage and symptoms are often limited to oral irritation. However, sap running down the throat can cause severe swelling and has been known to lead to fatal asphyxiation in rare cases. Emergency veterinary treatment is usually successful in keeping the airways open and ensuring that insoluble oxalate poisoning doesn’t cause life-threatening symptoms.

Insoluble oxalates are needle-like crystals found in the stems, leaves, and sap of many plants. These toxins are not absorbed into the bloodstream, but they can cause pain, inflammation, and swelling when they embed in the skin or in the lining of the gastrointestinal tract.

These are the signs you may see in a dog that has eaten a plant containing insoluble oxalate crystals.

• Hypersalivation
• Oral pain (pawing at the mouth or vocal expression)
• Hoarse barking
• Vomiting
• Lack of appetite
• Difficulty breathing

Types

Many common houseplants contain insoluble oxalates. These are some examples.

• Dumb cane and other dieffenbachia species
• Philodendron plant (many different Philodendron species)
• Swiss cheese plant or fruit salad Plant (Monstera deliciosa and other Monstera species)
• Peace lily (Spathiphyllum cochlearispathum and other Spathiphyllum species)
• Calla lily (Zantedeschia aethiopica)
• Chinese evergreen (Aglaonema species)
• Elephant’s ear (Colocasia species)
• Flamingo plant (Anthurium species)
• Arrowhead plant or African evergreen (Syngonium podophyllum)
• Pothos or devil’s ivy (Epipremnum aureum)
• Schefflera or umbrella tree (Schefflera actinophylla or Schefflera arboricola)

Some important risk factors for insoluble oxalate poisoning.

• One of the plants listed above growing in your house may contain the needle-like crystals that cause pain when chewed or swallowed
• Dogs that like to chew on plants may continue to bite and swallow despite the pain
• Small dogs may be affected more upon ingestion due to low weight and ability to process the plant toxins

A history of eating or chewing on a plant that contains insoluble oxalates is the most effective way of diagnosing the condition. Since many of these plants are grown indoors, owners often find chewed leaves or stems immediately. If you notice oral pain or other abnormal symptoms in your dog, it’s a good idea to check your houseplants for signs of chewing. If you aren’t sure what your dog has eaten, the veterinarian may be able to identify the problem based on symptoms and elimination of other potential causes.

Call an emergency veterinarian or a poison helpline any time your dog eats a plant that could be toxic. Be prepared with a description of the plant, including the species name if you know it. Your dog’s size and weight, and an estimate of the amount ingested will also be relevant to the severity of toxicity. If your dog is having trouble breathing, in-office emergency treatment will be needed immediately. Bring along a sample of the plant for accurate identification. Use gloves when handling the plant and transport the sample in a sealed plastic bag.

For immediate first-aid, rinse your dog’s mouth with milk or water and encourage him to drink liquids. Milk will be especially effective since the oxalate crystals will bind to the calcium in the milk and reduce pain and irritation in the mouth.

At the veterinary office, breathing difficulty will be the immediate concern. If there is significant swelling in the pharynx or esophagus, a tube may be inserted to assist with respiration or additional oxygen may be given through a mask. 

Milder symptoms will be treated also. Steroids or other anti-inflammatory medication can help to reduce swelling. Medications may be prescribed to coat the stomach lining and minimize gastrointestinal problems if your dog has swallowed enough material to cause vomiting. Topical ointments can help skin irritation heal faster.

In general, the prognosis for insoluble oxalate poisoning is good. Most cases are associated with only mild symptoms which will resolve themselves in 24 hours with no permanent damage. Even severe poisoning can usually be treated by a veterinarian. In rare cases, a delay or a poor response to treatment has resulted in fatality. Your dog’s chances of recovery will be best determined by a veterinarian.

The best way to manage the condition is to avoid having plants that contain insoluble oxalates in your house, however this may not be possible for everyone. If you really like houseplants, discuss safer species with your veterinarian. The risk involved with keeping a houseplant that contains insoluble oxalates will depend on your dog. Many dogs have a good instinct for toxic plants and can be trained to avoid them. Others may have frequent problems. If you do decide to keep these plants, put them in a place your dog rarely goes. Plant dog-safe wheat grass in pots and encourage your dog to chew on this so he won’t be interested in biting into other plants. Always warn visitors with dogs or children about the presence of toxic plants in your house.