The photosensitization that takes place in the skin of a cat who has consumed buckwheat manifests as severe skin irritation. Cats who have hypersensitive skin, or who have short or white coats are more at risk for issues stemming from eating buckwheat. The leaves, stems, and flowers of the plant can be toxic, although the leaves are the most potent by far. Skin reactions can lead to the development of ulcers which create the risk of a secondary bacterial infection forming in the open sores. This also allows for the possibility of systemic infection to spread throughout the cat. 

Buckwheat is a green, leafy plant that belongs to the Polygonaceae family of vegetation. It is also known in some parts as “Japanese knotweed”. Buckwheat's Latin name is Fagopyrum, for the presence of a fluorescent pigment found within it known as fagopyrin. This pigment is a type of phototoxin, which is composed of chemicals that affect the skin, making it very sensitive to light. Because of these phototoxins, eating large amounts can be harmful to cats. 

Skin issues and general dermatitis often set in after the cat has been exposed to sunlight. This is because the phototoxins need UV light to complete their chemical reaction in the body. All signs to watch for are listed as follows:

Cats may be exposed to buckwheat in several ways. The leaves and stems of the plant are often ground into a flour for use in both human and cat diets. Some cat treats may contain buckwheat flour. Because of their health benefits, many people grow buckwheat sprouts in herb gardens or inside the home. This means that both indoor and outdoor cats may come into contact with buckwheat, either from the plant itself, or from foods containing buckwheat flour. A large amount must be eaten for a toxic effect to occur.

If your cat has developed symptoms of buckwheat poisoning, it is best to bring it in for an assessment by a veterinarian. It is a good idea to bring the cat's full medical history to help the vet differentiate a potential poisoning from a health issue that already existed in your cat. You will be asked extensively about your cat's diet, including all ingredients in the cat's food and treats. You may also be asked about how much access your cat has to the outdoors.

A complete physical examination will be performed on your cat. During this examination, all symptoms will be noted in an attempt to match them to the closest fitting health issue. A skin scraping may be taken for further testing to differentiate buckwheat poisoning from an allergic reaction or other forms of dermatitis. The sample may also have a bacterial culture performed on it, identifying any harmful bacteria that could be causing a secondary infection in the cat.

The goal of the initial treatment will be to lessen the severity of any symptoms that have appeared. Any secondary issues may require further treatment.

Topical Therapy 

Bathing the cat with special, prescribed shampoos or administering ointment on the affected areas of the skin can provide great relief to itching and irritation. 

If a bacterial infection has been identified in the ulcerations on the skin, a course of antibiotics may be prescribed. These will rid the body of the harmful bacteria and prevent a systemic infection from taking hold of the cat. Prescriptions generally last from one to four weeks. 

Once buckwheat has been identified as the underlying problem in your cat's skin issues, be sure to remove all foods or treats that contain flour from the plant. It may be the safest course of action to also remove any buckwheat sprouts growing in your home or garden. Keeping your cat indoors can prevent it from gaining access to the plant in other people's gardens. 

Often the redness and rashes will clear up in a few hours after consumption has been stopped. It can take a few days for the general irritation to leave your cat's skin. A follow-up appointment may be needed if a bacterial infection was found, to ensure that the antibiotics have eradicated the bacteria from the cat.