Redness in the lower teeth of infants may be caused by apical fistula, gingivitis, local trauma, or by the imminent eruption of a tooth, etc. It is recommended to go to the hospital for specific examination and treatment. Inflammation at the root tip of a tooth that has not been treated for a long period of time may become pus-filled and infected and stimulate the gums at the tip of the root to produce a fistula, which can sometimes be swollen and not obvious and look like a red. If teeth are not brushed properly and oral hygiene is poor, the gums may develop localized inflammation with a reddish appearance. Frustration of the gums by hard foods or hard toys. When a tooth is about to erupt, a reddish color may appear in the corresponding position. Generally, you can take a picture to confirm and wait for the tooth to erupt. It is recommended to consult a doctor in time.