Canis ISSN: 2398-2942

Allium species poisoning


  • A large plant group of mostly perennial bulbous herbs with characteristic aroma.
  • Group includes onion, spring onion, shallots, field garlic, garlic, chives, leeks, wild or wood garlic, crow or false garlic.
  • All parts of the plants should be considered toxic.
  • The onion (Allium cepa) is the most significant toxicologically in dogs.
  • Signs: gastrointestinal effects, dehydration and subsequent development of hemolytic anemia and Heinz body formation.
  • Diagnosis: signs and case history.
  • Treatment: gastric decontamination if appropriate, with symptomatic and supportive care. Emphasis on addressing a potential hemolytic anemia.
  • Prognosis: fatal cases are rare, even in dogs with predisposing factors.



  • Ingestion of plants or plant extracts.
  • Note that cooked plant material may still be hazardous.

Predisposing factors

  • Some dogs appear particularly susceptible to ingestion of plants from this group.


  • Some dogs appear at greater risk. These dogs possess erythrocytes with inherited high sodium-potassium ATPase activity, high potassium and low sodium concentrations, in addition to accumulation of reduced glutathione, glutamate, and aspartate (HK dogs).
  • These dogs are more likely to develop severe hemolytic anemia and methaemoglobinemia.
  • These severe clinical features may have an early onset (1-2days) in these dogs.


  • Toxic mechanism not fully elucidated and probably multifactorial.
  • Toxins are thought to be a group of structurally similarn-propyl disufides and thiosulfinate compounds.
  • N-propyl disulphide depletes glucose-6-phosphate dehydrogenase (G6PD) within erythrocytes diminishing the protective effect of glutathione, as this remains in its oxidized state.
  • In this state glutathione forms mixed sulphide bonds with hemoglobin and precipitates within the cell resulting in the formation of Heinz bodies.
  • These affected cells are usually removed from circulation by the reticuloendothelial system, thereby inducing anemia.
  • There is evidence to suggest that there are other oxidative extracts within the plant material that may directly induce methaemoglobinemia and Heinz body formation.


  • Onset of signs is variable, although signs are usually apparent within 6-24 hours.
  • Signs of hemolytic anemia or methaemoglobinemia may be delayed for 1-5 days.
  • Full recovery may take 7 days or more.
  • Dogs with the predisposing factors may develop severe signs within 24-48 hours.


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Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Yamoto O & Maede Y (1992) Susceptibility to onion-induced haemolysis in dogs with heredity high erythrocyte reduced glutathione and potassium concentrations. Am J Vet Res 53B, 134-137 PubMed.
  • Miyata D (1990) Isolation of a new phenolic compound from the onion (Allium cepa L.) and its oxidative effect on erythrocytes. Jap J Vet Res 38 (2), 65 VetMedResource.
  • Kobayashi K (1987) The haemolytic effect of onions on canine erythrocytes associated with inherited high Na,K-ATPase activity. Jap J Vet Res 35 (2), 137 HUSCAP.
  • Solter P & Scott R (1987) Onion ingestion and subsequent Heinz body anaemia in a dog: a case report. JAAHA 23 (5), 544-546 VetMedResource.
  • Smith C H & Ellison R S (1986) Concurrent onion poisoning and haematuria in a dog. NZ Vet J 34 (5), 77-78 PubMed.
  • Kay J M (1983) Onion toxicity in a dog. Modern Veterinary Practice 64 (6), 477-478 VetMedResource.

Other sources of information

  • Cooper M R & Johnson A W (1998) Poisonous plants and Fungi in Britain: Animal and Human Poisoning. Second Edition. The Stationery Office, London, pp 31-34 ISBN 0 11 242981 5