The following substances are considered to be non-toxic, although they may cause mild gastrointestinal upset in some animals: (michigananimalhospital.com)
Although they are very rare, side effects are said to come in the form of mild gastrointestinal upset, contact dermatitis, or diarrhea. (endalldisease.com)
Both cats and dogs can be affected from eating lilies, however dogs will only exhibit mild gastrointestinal upset whereas 2 - 3 leaves for a cat may be lethal. (veterinaryemergencyhospitalofwesttoronto.com)