Sweet pea plants, known scientifically as *Lathyrus odoratus*, are a popular flowering annual climber prized for their vibrant, fragrant blossoms. From a botanical perspective, it is crucial to distinguish them from the edible pea plant (*Pisum sativum*) whose pods and seeds are consumed by humans. The sweet pea plant is considered toxic to both cats and dogs. The primary toxic principle in sweet peas is a compound called beta-aminopropionitrile. This substance is found throughout the plant but is most concentrated in the mature seeds. Beta-aminopropionitrile can interfere with collagen formation, potentially leading to musculoskeletal and neurological problems if ingested in significant quantities.
All parts of the sweet pea plant contain the toxic compound, posing a risk if ingested by pets. However, the level of toxicity is not uniform across the plant. The highest concentration of beta-aminopropionitrile is found in the mature seeds and seed pods. Therefore, a pet chewing on a few leaves or flowers may experience a milder reaction compared to one that consumes a large number of seeds. The overall risk is generally considered mild to moderate. A small, curious nibble might only cause minor gastrointestinal upset, while ingestion of a large volume of seeds could lead to more severe, though rare, neurological conditions such as weakness, lethargy, and seizures.
The beta-aminopropionitrile toxin in sweet peas functions as a lathyrogen. It inhibits the enzyme lysyl oxidase, which is essential for the proper cross-linking of collagen and elastin fibers in connective tissues. This disruption can weaken structural proteins in the body. In practical terms for a cat or dog, this most commonly manifests as acute gastrointestinal irritation. The most frequently observed clinical signs of sweet pea poisoning include vomiting, diarrhea (which may contain blood), and lethargy. With significant seed consumption, the toxin can affect the nervous system, potentially leading to tremors, weakness, an unsteady gait (ataxia), and even seizures in severe cases.
When identifying potential plant toxicity, it is important for pet owners to be aware of similar-looking plants. The perennial sweet pea (*Lathyrus latifolius*), a related species, also contains similar toxic compounds and poses the same risk to pets as *Lathyrus odoratus*. This contrasts sharply with the garden vegetable pea plant (*Pisum sativum*), which is non-toxic. The key identifier is that edible peas are grown for their pods and seeds, which are typically plump and meant for consumption, whereas sweet peas are cultivated for their ornamental flowers and their pods are flatter and inedible. Always err on the side of caution and prevent pets from accessing any unknown flowering vines.
