Onion Toxicity

by: Dr. Rebecca Lundeen from Oswego Animal Hospital

Winnie is a 13 year old female Bichon Frise who was presented for examination at Oswego Animal Hospital for sudden collapse and weakness. Winnie had ingested a large Spanish onion one week prior to this visit. At that time she was taken to CARE Emergency Services. No significant findings were noted on physical examination except a previously diagnosed low grade (Grade II/VI) heart murmur. Vomiting was induced and a large amount of onion/digesta was noted. Activated charcoal was administered to absorb potential remaining toxins.

According to the owner Winnie had been behaving normally until the morning of presentation at Oswego Animal Hospital. The owner witnessed several episodes of collapse and felt that Winnie seemed very weak and more lethargic than usual.

On physical examination, Winnie was quiet but alert and responsive. Her gums were very pale. Winnie’s heart murmur appeared to be louder (Grade III-IV/VI) than noted previously. No other significant findings were noted on physical exam.

Bloodwork and radiographs were performed. The only abnormal radiographic finding was a mildly enlarged heart. On her bloodwork, Winnie’s red blood cell count was very low. Her hematocrit level, which is roughly equivalent to the percentage of red blood cells in the blood, was 15%. A normal reference range for this value is approximately 36-60%. The reticulocyte count was also elevated, which indicated that Winnie’s body was regenerating and producing more red blood cells.

It was discussed with the owner that Winnie’s weakness and episodes of collapse were most likely secondary to her low red blood cell count. Destruction of red blood cells can be a side effect of onion toxicity.

A full diagnostic work-up of Winnie’s heart condition as well as hospitalization and possible blood transfusion were recommended. The owner declined and elected to continue to monitor Winnie at home in the hope that her body would be able to replace her red blood cells. Winnie’s physical activity was limited and she returned for regular recheck visits to closely monitor her hematocrit levels. Over the next several weeks her red blood cell numbers slowly returned to normal. Her heart murmur also returned to its original low grade (Grade II) as her red blood cell count increased. She has had no further episodes of collapse or weakness and is doing well at home with her family.

There are many different foods, such as onions, which can have negative effects on our pets despite being safe for people. Please consult your veterinarian regarding potential toxicity and further recommendations for any item that your pet may have ingested.