A black hard knot falling from the navel with a foul odor may be related to inadequate cleaning, and in the case of infants it may be inflammation of the umbilical cord stump. Umbilical cord inflammation can also have a foul odor, mostly accompanied by redness, swelling and discharge. In the deeper navel of the population, due to the navel folds or usual cleaning is not in place, the skin epidermal metabolism and sweat stains, dirt, etc. accumulated in the navel, the formation of smelly black lumps or hard knots, drying can be dropped. After the delivery of the fetus will be ligated umbilical cord, then the umbilical cord stump healing scars or scabs, improper care can cause inflammation, bacterial growth triggered inflammation, odor. It is recommended to pay attention to cleanliness, use warm water or alcohol to gently wipe the localization. If the navel local redness, swelling, pain, odor and other conditions are recommended to go to the hospital in a timely manner, as prescribed by the doctor for treatment.