A five-year-old baby with a lump on the gums may be related to poor oral hygiene, or it may be due to gingivitis, periapical inflammation and other causes. 1. Poor oral hygiene: 5-year-old babies who usually have poor oral hygiene, morning and evening did not develop a good habit of brushing their teeth, in the long run, it may cause gingival hyperplasia, which will show a lump on the gums, and the color is usually presented as dark red or bright red. 2. Gingivitis: the disease is usually due to plaque caused by the inflammatory reaction of the gum tissue, under the stimulation of inflammation, may cause a lump on the gums, may also be accompanied by bleeding gums, bad breath and other symptoms. 3. Periapical inflammation: usually due to the inflammatory reaction caused by bacterial infection of the tissues around the root tip, under the stimulation of inflammatory factors, it may lead to a pimple on the gums, and may also be accompanied by symptoms such as occlusal pain, swelling and pain. Five-year-old baby gums have a pimple, may also be caused by other reasons, it is recommended to consult a doctor as soon as possible, clear causes, give targeted treatment.