Chemical Composition: Commercial lawn fertilizers often contain substances such as nitrogen, phosphorus, potassium, herbicides, and pesticides. While these elements are great for grass growth, they can harm pets if ingested or inhaled.

Lawn pesticides can be toxic to dogs, mainly because they will walk through the grass and more then likely lick their feet soon after thus ingesting the toxin. The skin contact alone may cause allergic reactions on the skin, but ingesting the toxin may cause issues much more severe.