If you have observed your dog sucking or nursing on your arms occasionally, then there is nothing to be alarmed about. The process of sucking comes out of their instincts and develops during breastfeeding.  If your dog feels comfortable with you and is at ease, it might suck on your arm to give itself the feeling of breastfeeding. This particular habit should not be encouraged, and it is better to stop it before it gives rise to any other problem.