Can’t they see the fleas? Or are fleas so microscopic that they can’t see them? My friend’s dog has fleas because she saw one but didn’t see anymore, then her other dog had “one” on her but when I went on here people said if there is one, there are tons more.My friend says her dogs do not have fleas, they just had one. So is my friend in denial or can you not see fleas?? Oh and I saw small black bugs on her walls and she laughed at me and said they weren’t fleas because fleas can’t fly. Is it true they can’t fly?