Clearly, you are inquiring as to whether or not just the smell of the dog, on your friend, would evoke a defensive reaction from the snake. In my opinion not very likely, but possible. If the snake is ordinarily "touchy" or jumpy, then it has an increased chance of freaking out on any alien or unusual odors or smells. For the most part though I wouldn't say that there is too much to worry about with a residual smell, no.
>>Suppose I live in a duplex the upstairs people have a dog and well the tenant is one of my good friends, suppose he came down one time, while my snake was out. Would the snake react to to the smell of dog on him. I know sometimes i'm full of ?'s but I'm curious and will not find out if I don't ask....thanks
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