Why do dogs sniff your hand before becoming friendly?

The idea of presenting the back of the hand for a dog to smell is a way of showing the dog that the human is friendly and is respecting the dog, think of it as a handshake; however, this act of social decorum really makes no difference to a dog because their powerful sense of smell has already detected all manner of scents and pheromones the human carries, such as adrenaline (which is exuded through the pores of the skin when a person is afraid or highly excited). Dogs can smell these scents several feet away without even having to make any form of bodily contact, so the practice of showing the hand to a dog is simply a movement of politeness on the human's part.

Next time you are meeting a new dog remember that before they get to your hand the dog will have already scanned your body posture, eye fixation ( do not make direct eye contact at first as this can be interpreted as a territorial challenge to the dog) and scent by the time you decide to approach or not. Their survival depends upon this assessment so be calm and relax; know that if a dog is approaching you in a friendly manner is most likely because he has determined you are trustworthy, even before you realise it in yourself.

Be calm. Be assertive. Be balanced.

Vibes.