Many people do not instantly notice these signals and a dog could be pushed into growling or baring teeth to tell you that they are not comfortable with the interaction.
It is advised that you do not put your face into the dog's face. A dog will not bite a face unless it is too close.
Hugging your dog can be scary, extended eye contact can cause your dog to display one or more of these signals.
You may also see these behaviours occuring in stressful situations, such as visitors at the property, or being in a very busy area on a walk, or dogs rushing over to them to interact.
Allow your dog to remove themself from the room if they start to display fearful signals.