Onion

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  Avoid
  Onion can damage red blood cells in dogs and may cause anemia.
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  Avoid
  Cats are especially sensitive to onion toxicity.
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• 

  Avoid
  Onion should not be fed to rabbits.
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• 

  Avoid
  Onion may irritate the digestive system and should be avoided.
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Sources

• ASPCA – People Foods to Avoid Feeding Your Pets