While smaller amounts may not cause harm, large amounts have the potential to be very dangerous, especially in a small animals, such as cats. The potassium oxalates contain dicarboxylic acid, which the body cannot break down, and is poured out with the urine. This acid can cause major damage to the cat's internal organs in large amounts. Calcium oxalates have an adverse effect on the kidneys, and form crystals within the urinary tract. While most dock poisonings are not fatal, if a severe reaction occurs, death can follow in as little as ten hours.

The scientific genus Rumex includes all forms of dock and sorrel plants. These plants are perennial herbs that can grow up to 3 feet in height. They belong to the Polygonaceae family, closely related to buckwheat. The dock plant is edible to humans in small amounts, and may be found in mixed green salads. The leaves are sour in taste, mostly due to the soluble potassium and calcium oxalate toxins found within them. 

If too much of the dock plant has been eaten, negative symptoms will begin to manifest two to six hours after consumption. If the leaf juices make contact with the cat's skin, irritation and other external issues may form. Signs to watch for include:

Dock and sorrel plants may be found growing in the wild or may be kept in herb gardens. The leaves may be brought in the home for human consumption. Outdoor cats may have more chance of exposure to the plants than indoor cats. The leaves of the plant are toxic and cause a burning sensation in the throat when too many have been eaten, which generally signals the animal to stop.

If symptoms of dock poisoning have begun to show in your cat, rush it to the nearest veterinary clinic or animal hospital immediately. Treatment to stabilize the animal may be given while a diagnosis is attempted. Provide your cat's full medical history to assist with the diagnostic process. It you witnessed the cat eating a plant before symptoms arose, but are unsure of what the plant was, bring a small clipping with you to be identified by the veterinarian. 

A complete physical examination will be performed on the cat. All symptoms will be noted to try and match them with any possible causes. Full blood work will be run, including a complete blood count and a biochemical profile. Calcium and potassium levels in the bloodstream will be measured. Urinalysis may show if the kidneys are functioning properly and if potassium oxalates are being expelled with the urine. Dock poisoning must be differentiated from other neuromuscular and kidney diseases.

Administering treatment in a fast manner offers the best chance for recovery from  dock poisoning. Symptoms may also be treated to keep the cat as comfortable as possible throughout the episode.

A solution high in calcium such as dilute calcium lactate or dilute calcium hydroxide (also known as lime water) will help to fight against the effects of potassium oxalates in the body. The cat may be encouraged to drink the solution, but more than likely the liquid will have to be given intravenously.

Gastric Lavage 

A stomach pumping via gastric lavage will help remove any remaining plant material from the body. The lavage may be performed using lime water to further halt the effects of potassium oxalates in the digestive tract. 

 If skin irritation has developed from exposure to dock leaf juices, bathing the cat using a medicated shampoo will ease itching immediately.

While dock poisoning can produce very severe reactions in cats, these are rare due to the large quantity that must be eaten before levels of toxicity are reached. Prompt treatment offers the best prognosis, so do not hesitate to bring your cat to a veterinarian if you even slightly suspect that it has been poisoned. 

It may be the safest option to keep dock and sorrel plants out of your gardens if you have cats. Refrain from leaving salads unattended in case your cat becomes curious. Keeping your cat indoors can help shelter it from possible exposure to these plants in other people's vegetable and herb gardens. It may also benefit to become familiar with plants that are toxic to your cat, so that you will be able to identify them if necessary.