According to the ASPCA, when dogs eat members of the onion family, such as shallots, onions, garlic and scallions, there is sometimes damage to red blood cells. Small amounts are typically not harmful, but larger portions are potentially dangerous. Stronger foods like garlic are more toxic than milder ones.
The ASPCA points out that dogs generally do not eat large quantities of raw onions or garlic. Concentrated, dehydrated forms of those foods, including powdered spices and soup mixes, are more likely to be eaten in toxic amounts. Symptoms, which often do not appear for three to five days after ingestion, include fatigue and orange or red urine. This is a dangerous condition that sometimes requires blood transfusions.