Bio Andrew âAndyâ Lambros is a web and graphic designer, developer, marketing expert and business consultant. He is the Co-founder and President of the Dream Builders Company, located just outside of Los Angeles, in Southern California.
I have a 3 year old with a sore in his mouth. It is between his upper lip and his gums at the very top. It looks like a white circle and it has a red streak coming down to his teeth.
Causes of Mouth Ulcers or Sores. 1  Canker Sores. The main cause of 1 or 2 mouth ulcers after age 5. 2  Hand-Foot-Mouth Disease. The most common cause of multiple ulcers in the mouth. 3  Herpes Simplex Virus (Cold sore virus). The first infection can be severe. 4  Cold Sores (Fever Blisters). Sores are only found outside the mouth on the outer lip. They recur 2 or 3 times a year in the same place. There are no ulcers inside the mouth. Adult cold sores are the cause of Herpes Simplex infections in young children. Occurs in 20% of teens and adults.