Onions, Garlic, Chives, Leek Plants (Allioideae)
Alliums such as onions, garlic, chives, and leeks are among the most popular ingredients in human cuisine. However, many pet owners are unaware that these very foods can be highly toxic to dogs and cats. Even small amounts – whether raw, cooked, or dried – can cause serious health problems. It is particularly problematic that the symptoms of poisoning often appear with a delay. In numerous cases, leftovers of seasoned foods, such as onion sauces or garlic bread, are offered as supposed treats – with potentially life-threatening consequences.
The most important facts at a glance
Onions, garlic, and other members of the Allioideae family are highly toxicToxic means "poisonous" and refers to substances that can have harmful effects on the body, including damage to organs, cells, or disruption of metabolic processes. to dogs and cats. The damage is caused by oxidative processes in the red blood cells, which can lead to hemolytic anemia and, in severe cases, death. Since symptoms often appear with a delay, early veterinary treatment is crucial. The prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop. varies depending on the severity, animal species, and reaction time. Conscious avoidance of these plants in pet nutrition is essential.
Causes, development and progression
All alliums are potentially toxicToxic means "poisonous" and refers to substances that can have harmful effects on the body, including damage to organs, cells, or disruption of metabolic processes. to dogs and cats.
A group of substances known as propyl disulfides is responsible.
These sulfur compounds appear to be readily absorbed through the gastrointestinalGastrointestinal refers to the gastrointestinal tract, a system that extends from the oral cavity to the anus and is responsible for the digestion of food and the absorption of nutrients. tract and then converted into highly reactive oxidizing agents.
Cooking, drying, and similar processes do not alter their effect.
The most common cause of poisoning is the unintentional feeding of foods containing ingredients from the Allium family. Particularly insidious: Even dried, powdered, or cooked forms retain their toxicToxic means "poisonous" and refers to substances that can have harmful effects on the body, including damage to organs, cells, or disruption of metabolic processes. effect. However, animals can also ingest these substances through dropped scraps, garbage bag contents, or compost piles. In some cases, garlic is deliberately used as a natural remedy for parasiteA parasite is an organism that lives on or in another living being (the host) and feeds at its expense. Parasites can cause a variety of diseases in animals and humans. control – which, from a veterinary perspective, is not only ineffective but dangerous.
Mechanism of action
Organosulfur compounds oxidize the blood pigment hemoglobinhemoglobin is an iron-containing protein in red blood cells responsible for transporting oxygen from the lungs to the body tissues and carbon dioxide back to the lungs. in red blood cells to methemoglobin, followed by associated instability of the red blood cells and increasing hemolysishemolysis is the process of red blood cell breakdown, releasing hemoglobin. It can be triggered by various factors, including certain diseases, toxins, or incompatible transfusions. (dissolution of red blood cells). As a result, anemia occurs.
Some dog breeds, such as the Akita Inu and Shiba Inu, are particularly susceptible to oxidative damage caused by onions due to genetically determined peculiarities in their erythrocytesErythrocytes, also known as red blood cells, are the most common blood cells in the human body. Their main function is to transport oxygen from the lungs to the tissues and carbon dioxide back to the lungs..
Cats, whose red blood cells are already very susceptible to oxidation, also react sensitively.
The toxicToxic means "poisonous" and refers to substances that can have harmful effects on the body, including damage to organs, cells, or disruption of metabolic processes. dose for onions is reached in dogs with an intake of 15 to 30 g/kg body weight and in cats with 5 g/kg body weight.
The toxicToxic means "poisonous" and refers to substances that can have harmful effects on the body, including damage to organs, cells, or disruption of metabolic processes. effect of alliums is based on organic sulfur compounds. In particular, N-propyldisulfide, allyl propyl sulfide, and thiosulfates attack red blood cells (erythrocytesErythrocytes, also known as red blood cells, are the most common blood cells in the human body. Their main function is to transport oxygen from the lungs to the tissues and carbon dioxide back to the lungs.). These substances create so-called oxidative stressStress refers to the state of an organism reacting to external stimuli or demands. In veterinary medicine, stress can have physical or psychological effects on animals, impacting their health and well-being. in the cells, lead to the formation of Heinz bodiesHeinz bodies are abnormal structures in red blood cells that result from the oxidative breakdown of hemoglobin. Their presence may indicate certain toxins, drugs, or diseases that lead to oxidative stress in dogs and cats. – which are degenerated hemoglobinhemoglobin is an iron-containing protein in red blood cells responsible for transporting oxygen from the lungs to the body tissues and carbon dioxide back to the lungs. structures – and ultimately cause the destructionDestruction means "demolition." In medicine, it refers to the destruction of cells, tissues, organs, or body parts. The growth of malignant Tumors is also usually accompanied by destruction of the surrounding tissue. of erythrocytesErythrocytes, also known as red blood cells, are the most common blood cells in the human body. Their main function is to transport oxygen from the lungs to the tissues and carbon dioxide back to the lungs. (hemolysishemolysis is the process of red blood cell breakdown, releasing hemoglobin. It can be triggered by various factors, including certain diseases, toxins, or incompatible transfusions.). Consequently, severe anemia can occur, which severely impairs oxygen transport in the body. Additionally, methemoglobin can form – a form of hemoglobinhemoglobin is an iron-containing protein in red blood cells responsible for transporting oxygen from the lungs to the body tissues and carbon dioxide back to the lungs. that can no longer transport oxygen.
Symptoms of intoxication
Symptoms of intoxication begin one day or sometimes several days after ingestionIngestion refers to the intake of substances through the mouth and their delivery to the digestive tract. In dogs and cats, the ingestion of toxic substances, foreign objects, or incompatible foods can lead to health problems..
The primaryPrimary refers to the first or original cause of a disease or condition, as opposed to secondary causes or symptoms that develop from it. symptoms to observe are:
- Loss of appetite
- Vomiting,
- DiarrheaDiarrhea refers to the condition of frequent, watery bowel movements, which can be a sign of infections, digestive disorders, or other health problems.
- Bauchschmerzen
- Anämie
- Pale or jaundiced (yellow) mucous membranes
- Weakness
- Increased heart rate
- Increased respiratoryRespiratory refers to breathing or the process of breathing. Respiratory diseases affect the respiratory tract and can impair the ability to breathe effectively. rate
- Hemoglobinuria (dark urine due to hemoglobinhemoglobin is an iron-containing protein in red blood cells responsible for transporting oxygen from the lungs to the body tissues and carbon dioxide back to the lungs. excretion)
- Presence of Heinz bodiesHeinz bodies are abnormal structures in red blood cells that result from the oxidative breakdown of hemoglobin. Their presence may indicate certain toxins, drugs, or diseases that lead to oxidative stress in dogs and cats. (clumps of blood pigment) in the erythrocytesErythrocytes, also known as red blood cells, are the most common blood cells in the human body. Their main function is to transport oxygen from the lungs to the tissues and carbon dioxide back to the lungs.
Death occurs due to lack of oxygen.
Diagnosis
For diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients., a precise medical historyThe medical history is the systematic collection of a patient's medical history through questioning. It includes information about previous illnesses, treatments, allergies, and lifestyle habits. is crucial: When and in what quantity was an allium ingested? Additionally, blood and urine tests provide important clues:
- The blood count often shows regenerative anemia with increased reticulocytosis.
- Specific is the detection of Heinz bodiesHeinz bodies are abnormal structures in red blood cells that result from the oxidative breakdown of hemoglobin. Their presence may indicate certain toxins, drugs, or diseases that lead to oxidative stress in dogs and cats. using dyes such as brilliant cresyl blue.
- In blood chemistry, elevated liver enzymesEnzymes are biological catalysts that accelerate specific chemical reactions in the body without being consumed. They play a crucial role in virtually all physiological processes. and bilirubinBilirubin is a yellow pigment that is produced when hemoglobin from red blood cells is broken down. It is further processed in the liver and then excreted via the bile. Elevated bilirubin levels may indicate liver dysfunction or impaired bile excretion. levels may be detectable.
- Urine analysis can reveal hemoglobinuria (free hemoglobinhemoglobin is an iron-containing protein in red blood cells responsible for transporting oxygen from the lungs to the body tissues and carbon dioxide back to the lungs. in the urine).
Imaging procedures are generally not necessary but can help rule out other causes in cases of unclear symptomatologySymptomatology refers to the entirety of symptoms associated with a particular disease or condition. It describes how a disease manifests itself externally..
Therapeutic principles
There is no antidoteAn antidote is a substance used to neutralize or reverse the harmful effects of poisoning or a drug overdose. Antidotes can be specific to certain poisons or have more general detoxifying effects.. Antioxidants (vitaminVitamins are organic compounds that are necessary in small amounts for the normal growth, development, and physiological function of the body. Vitamins must mostly be obtained through food, as the body cannot produce them or not in sufficient quantities. E and acetylcysteine) can be used. Therapeutic measures vary depending on the amount ingested and the animal’s clinical condition. If ingestionIngestion refers to the intake of substances through the mouth and their delivery to the digestive tract. In dogs and cats, the ingestion of toxic substances, foreign objects, or incompatible foods can lead to health problems. occurred recently and no symptoms are present yet, immediate decontaminationDecontamination refers to the removal of toxic substances or pathogens from a living being, object, or environment to prevent or treat poisoning or infection. of the digestive tract is performed by gastric and intestinalIntestinal refers to the intestine, the part of the digestive tract that extends from the stomach to the anus. Intestinal diseases affect the small and/or large intestine. emptying. This means inducing vomiting and administering activated charcoalActivated charcoal is a fine-pored, highly adsorbing material commonly used in veterinary medicine to treat poisoning. It binds toxins in the gastrointestinal tract to prevent their absorption into the body. to prevent further absorptionAbsorption refers to the uptake of substances by living cells or tissues. In the context of veterinary medicine, it often refers to the absorption of nutrients, drugs, or toxins from the digestive tract into the bloodstream. of toxins. DecontaminationDecontamination refers to the removal of toxic substances or pathogens from a living being, object, or environment to prevent or treat poisoning or infection. should ideally take place within 2 hours of ingesting the poison. Plant parts sometimes remain in the stomach for a longer period, so inducing vomiting or gastric lavageLavage is a rinsing procedure that uses a liquid to clean a body cavity, organ, or wound. In veterinary medicine, lavage can be used, for example, for gastric lavage or to clean an infected wound. may still be useful at a later time.
In symptomatic cases, intensive symptomatic and supportiveSupportive refers to supportive treatments that aim to alleviate symptoms and improve quality of life without directly treating the underlying cause of the disease. therapyTherapy refers to the treatment of diseases or disorders with the aim of alleviating symptoms, promoting healing, or improving quality of life. Therapies can be medicinal, surgical, or through other medical interventions. is required:
- Intravenous fluid therapyTherapy refers to the treatment of diseases or disorders with the aim of alleviating symptoms, promoting healing, or improving quality of life. Therapies can be medicinal, surgical, or through other medical interventions. to stabilize circulation, improve renal blood flow, and promote hemoglobinhemoglobin is an iron-containing protein in red blood cells responsible for transporting oxygen from the lungs to the body tissues and carbon dioxide back to the lungs. excretion
- Oxygen administration for severe anemia or methemoglobinemia
- Blood transfusion in severe hemolysishemolysis is the process of red blood cell breakdown, releasing hemoglobin. It can be triggered by various factors, including certain diseases, toxins, or incompatible transfusions. or if clinical symptoms indicate significant hypoxiaHypoxia refers to a condition in which the body or a part of the body is not supplied with enough oxygen. This can lead to various symptoms, including shortness of breath, confusion, and in severe cases, organ failure.
- Administration of antioxidants such as N-acetylcysteine to reduce oxidative cell damage
All measures should be closely monitored and accompanied by repeated blood count checks.
Prognosis & follow-up care
The prognosis is generally good. It strongly depends on the timing of diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients., the amount of toxinA toxin is a poison produced by living cells or organisms that can be harmful to the body upon contact or ingestion. Toxins can originate from bacteria, plants, animals, or fungi. ingested, and the animal’s general condition. Mild to moderate intoxications with early treatment usually proceed without complications. In severe cases with significant hemolysishemolysis is the process of red blood cell breakdown, releasing hemoglobin. It can be triggered by various factors, including certain diseases, toxins, or incompatible transfusions., however, the prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop. can be guarded to poor – especially if accompanying organ dysfunctions such as liver insufficiencyInsufficiency refers to the inadequate function or performance of an organ or system. This can include, for example, heart failure, kidney failure, or venous insufficiency. occur.
Follow-up care includes regular blood count checks for at least one week, or longer if necessary. Full recovery can take up to 14 days. Owners should be informed about the risk of relapse with repeated ingestionIngestion refers to the intake of substances through the mouth and their delivery to the digestive tract. In dogs and cats, the ingestion of toxic substances, foreign objects, or incompatible foods can lead to health problems..
Research outlook
Despite the well-documented toxicityToxicity is the measure of a substance's harmfulness or poisonousness. Toxicity can vary depending on the dose, route of exposure, and individual sensitivity. of alliums in dogs and cats, there are still some open questions in research that are important for veterinary practice:
Detailed molecular mechanisms:
Although it is known that sulfur compounds such as N-propyldisulfide induce oxidative stressStress refers to the state of an organism reacting to external stimuli or demands. In veterinary medicine, stress can have physical or psychological effects on animals, impacting their health and well-being. in erythrocytesErythrocytes, also known as red blood cells, are the most common blood cells in the human body. Their main function is to transport oxygen from the lungs to the tissues and carbon dioxide back to the lungs., the exact molecular signaling pathways leading to Heinz body formation, membrane damage, and apoptosis have not yet been fully elucidated. Further studies could contribute to the development of targeted antidotes.
Interindividual sensitivity:
The pronounced individual variability in sensitivity to Allium toxins suggests that genetic factors or differences in antioxidant capacity play a role. Future genetic or metabolomic analyses could contribute to risk assessment.
Different toxicityToxicity is the measure of a substance's harmfulness or poisonousness. Toxicity can vary depending on the dose, route of exposure, and individual sensitivity. depending on Allium species:
There is evidence that garlic is more toxicToxic means "poisonous" and refers to substances that can have harmful effects on the body, including damage to organs, cells, or disruption of metabolic processes. than onions due to higher concentrations of thiosulfates. Nevertheless, comprehensive quantitative comparisons of the toxicityToxicity is the measure of a substance's harmfulness or poisonousness. Toxicity can vary depending on the dose, route of exposure, and individual sensitivity. of various Allium species in relation to dogs and cats are lacking.
Optimization of diagnostics and therapyTherapy refers to the treatment of diseases or disorders with the aim of alleviating symptoms, promoting healing, or improving quality of life. Therapies can be medicinal, surgical, or through other medical interventions.:
The development of faster diagnostic tests for determining Heinz bodiesHeinz bodies are abnormal structures in red blood cells that result from the oxidative breakdown of hemoglobin. Their presence may indicate certain toxins, drugs, or diseases that lead to oxidative stress in dogs and cats. or cellularCellular refers to cells or consisting of cells. In biology and medicine, it refers to processes, structures, or functions that occur at the level of individual cells. oxidation markers in clinical practice could improve early diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients.. The therapeutic efficacy of new antioxidant combinations (e.g., N-acetylcysteine, vitaminVitamins are organic compounds that are necessary in small amounts for the normal growth, development, and physiological function of the body. Vitamins must mostly be obtained through food, as the body cannot produce them or not in sufficient quantities. E, S-adenosylmethionine) is also currently being further investigated.
Education and preventionPrevention includes measures taken to prevent diseases or injuries. In veterinary medicine, this includes vaccinations, parasite control, and health monitoring.:
Despite increasing awareness of the issue, pet owner education remains insufficient. Future research projects in behavioral and consumer analysis could help develop effective preventionPrevention includes measures taken to prevent diseases or injuries. In veterinary medicine, this includes vaccinations, parasite control, and health monitoring. strategies to reduce poisoning by alliums.
Frequently asked questions (FAQs)
1. From what amount are onions dangerous for dogs?
As little as 5 g/kg body weight can cause symptoms – about half an onion for a 10 kg dog.
2. Are cooked or dried onions less toxicToxic means "poisonous" and refers to substances that can have harmful effects on the body, including damage to organs, cells, or disruption of metabolic processes.?
No. The toxicToxic means "poisonous" and refers to substances that can have harmful effects on the body, including damage to organs, cells, or disruption of metabolic processes. compounds remain active even after heat treatment or drying.
3. Are small amounts of garlic harmless for tick preventionPrevention includes measures taken to prevent diseases or injuries. In veterinary medicine, this includes vaccinations, parasite control, and health monitoring.?
No. This practice is not evidence-based and can be harmful to health.
4. What symptoms appear first?
Symptoms often begin with apathyApathy refers to a state of indifference and reduced interest or lack of emotional involvement in activities or events that would normally arouse interest., vomiting, and dark urine within 24–48 hours.
5. Can onion poisoning be reliably detected by a blood testA blood test is a laboratory procedure in which blood is drawn and analyzed to obtain information about the body's health. It can include various parameters such as blood sugar, blood count, liver and kidney values.?
Yes. Heinz bodiesHeinz bodies are abnormal structures in red blood cells that result from the oxidative breakdown of hemoglobin. Their presence may indicate certain toxins, drugs, or diseases that lead to oxidative stress in dogs and cats. in the blood smear and regenerative anemia are typical findings.
6. What to do if my dog has eaten onions?
Seek veterinary help immediately. Do not use home remedies.
7. Why are cats more sensitive?
Their red blood cells are particularly susceptible to oxidative damage, and they lack an effective detoxification system.
8. Can symptoms be treated at home?
No. Professional medical care is essential.
9. How long does recovery take?
Full recovery can take up to two weeks, depending on the severity of the poisoning.
10. Can animals get sick from onions multipleMultiple means manifold or repeated and is used to describe conditions or events that occur in multiple instances or at different locations. In veterinary medicine, this may indicate multiple lesions, tumors, or other pathological changes. times?
Yes. Sensitivity persists, and even small amounts can cause damage again.
Literature
- Cope, R. B., 2005. Allium species poisoning in dogs and cats. Veterinary Medicine, 100(6), pages 428–432.
- Gwaltney-Brant, S., 2012. Allium species toxicosis in dogs and cats. Vet Clin North Am Small Anim Pract, 42(2), pages 373–382. Available at: https://doi.org/10.1016/j.cvsm.2011.12.007.
- Handl, S. and Iben, C., 2008. ToxicToxic means "poisonous" and refers to substances that can have harmful effects on the body, including damage to organs, cells, or disruption of metabolic processes. foods for small animals – a literature review. Vet. Med. Austria / Wiener Tierärztliche Monatsschrift, 95, pages 235–242.
- Koyama, K., Fujita, Y., Inoue, K., Nakaoka, R., Okita, M. and Tsuchitani, M., 2006. Hemolytic anemia in dogs and cats induced by garlic. Journal of Veterinary Medical Science, 68(2), pages 165–171.
- Lee, J. A., Yamato, O., Tajima, M., Kuraoka, M., Omae, S. and Maede, Y., 2000. Onion toxicity in dogs: a retrospective study. Australian Veterinary Journal, 78(6), pages 434–436.
- Löwe, G. and Löwe, O., 2021. Poisoning in dogs and cats – A veterinary Guides. 2nd Edition. Kreuztal: Kynos-Verlag. 208 pages.
- Müller, M., 2019. Oxidative damage by alliums: An underestimated risk for dogs and cats. Vet Journal, 33(5), pages 220–226.
- Vetpharm – Toxicological database of the University of Zurich. Plant data sheet for Allium species. Available online at: https://www.vetpharm.uzh.ch/giftdb/pflanzen/0049_tvm.htm.