Zoopharmacognosy..."zoo" = animal, "pharmaco" = remedy, "gnosy" = knowing. This is a word used to describe the behaviour of when an animal apparently uses plants, soils and insects through self medicating, to prevent or reduce harmful effects of bacteria, virus, or toxins that may have got into their bodies. They instinctly know which plant will help them. The understanding is that the dog's sense of smell will send the message to their brain, which will indicate to them what they may "need". I guess you may have seen this when dogs eat a particular grass that often results in them being sick, or when they dig for grass roots. Certain plants and herbs work for different aspects of the dog, from behavioural issues right through to physical conditions.