Allium Toxicity (Onion and Garlic)

Allium toxicity refers to a form of poisoning that can occur when dogs or cats eat onions, garlic, leeks, chives, or related plants. These foods contain compounds that damage red blood cells in a way that causes them to break down more rapidly than usual. The effect is dose-dependent and cumulative, so toxicity can develop after a single large exposure or repeated smaller amounts over time. Owners most often arrive at this topic after their pet has eaten something containing onion or garlic—whether raw, cooked, powdered, or as an ingredient in human food—and they are wondering what signs to watch for or what the timeframe of concern might be. Some pets show no immediate change, while others may develop lethargy, pale gums, dark urine, or reduced appetite in the days following exposure. This page explores the signals that may appear after allium exposure, the mechanism by which these plants affect red blood cells, the investigations that help assess the degree of anaemia or oxidative damage, and the range of approaches used to support affected animals depending on severity.