There's no one answer to this question since every dog is different and can be scared of different things. However, some common triggers for canine fear include loud noises, unfamiliar people or animals, being left alone and being in new, or unusual environments. If you notice your dog exhibiting any signs of fear or anxiety - including panting, shaking, cowering or clinging to you - it's important to remain calm and provide reassurance. Approach your dog slowly and speak in a soft voice until he or she feels better. Never punish a scared dog as that will only make the problem worse. If your dog's fears are severe or consistently impacting their quality of life, it's best to consult with a veterinarian or animal behavior specialist to help resolve their fears.