A lot of cats lick their owner’s hair, or even their beard and brows! This strange behaviour to humans can be easily explained: Cats groom the head area of their “preferred peers”.
Grooming is hence simply a sign of feline affection! Congratulations: your cat has selected you into this usually very selective “preferred peers” group. You will notice that your cat usually grooms your hair when you are lying down or when you are asleep, which are periods he considers to be appropriate for “affection grooming”. If he instead « grooms » or « eats » your hair when you are busy and active, it is more likely that this behaviour has more to do with him being playful.
Cats groom their peers for another reason: Territoriality. Your cat wants to remove other scents and debris from your “fur”, so that you smell like his own. This is an attention reserved to member of his “pack”, or to members who he wishes would be part of his pack.
While we can be pleased to deserve such attention at first, cat drool in our hair or a rough tongue on our delicate skin usually is not as much appreciated as our cat thinks.
What can we do to stop this behaviour?
Gently pushing your cat away or petting him back is not going to give him the message you want. He will instead perceive this attention as a sign of affection, making it more likely that he will continue to lick your hair. Any attention can in fact be perceived as affection and therefore reinforce this behaviour.
Instead, move your head away from your cat when he starts grooming your hair. Cats remove themselves from situations they do not like, so this reaction is a very natural and clear message for them.
A repulsive could also help if your cat is very insistent! Cats usually despise the smell of citrus, which makes any hair products with a citrus smell an effective repulsive for your cat.