Avocado (all parts) - the toxic ingredient in avocado is called persin (toxic amount unknown). Symptoms include difficulty breathing, abdominal enlargement, abnormal fluid accumulations in the chest, abdomen and sac around the heart.
Pear pips, the kernels of plums, peaches and apricots, apple core pips (contain cyanogenic glycosides resulting in cyanide posioning)
Potato peelings and green looking potatoes
Rhubarb leaves
Mouldy/spoiled foods(keep garbage lid firmly on)
Alcohol
Yeast dough
Coffee grounds, beans & tea (caffeine)
Hops (used in home brewing)
Tomato leaves & stems (green parts)
Broccoli (in large amounts)
Raisins and grapes
Cigarettes, tobacco, cigars
Xylitol (sweetener often found in sugar-free gum)
Cooked bones - they can splinter and cause gut perforation, as well as blockages in the intestine, tooth fractures, and cooked chop bones can get stuck across the roof of the mouth
Corn cobs - a common cause of intestinal blockage requiring surgical removal