Of all the household items that might be toxic to dogs, the lowly penny may be something you haven’t considered. According to the ASPCA Poison Control Center, however, American pennies minted after 1981 contain significant quantities of zinc. When ingested, excess zinc is absorbed through the gastrointestinal tract, and causes red blood cells to break apart. The result is anemia. Affected dogs will experience lethargy, vomiting and diarrhea, wine-colored urine and yellowing of the skin and gums.