The dog will see something unclean?

Dogs can not see unclean things, this is superstition, scientifically speaking, mainly because the dog’s sense of hearing and smell is very developed, so the slightest change in the environment, will trigger the dog’s abnormal reaction, such as suddenly barking into the air, may be frightened, or smelled a special smell. The dog’s eyesight is not good, equivalent to 0.3 of human eyesight, so dogs rely heavily on smell and hearing, although dogs do not speak, but can judge the owner’s meaning through the size of the master’s voice and euphemism of the small changes, and even through the smell to distinguish whether the owner is sick. So when the dog barked inexplicably at the air or objects, it was probably just because it smelled an unusual odor or was frightened, and for the purpose of protecting the owner, it barked loudly to achieve the purpose of warning.