If a blister is found present inside the mouth of a one year old baby, there are two diseases that are considered more common, the first being herpes simplex and the second being hand, foot and mouth disease. Oral herpes simplex, which is caused by herpes simplex virus infection, occurs mainly in the oral mucosa. When this type of herpes simplex appears inside the baby’s mouth, systemic antiviral therapy with oral acyclovir can be administered. After the blisters rupture, ulcers will form and the child will experience significant pain, at this time, you can spray open throat sword spray locally. Chlorhexidine gargle is also effective in reducing bacteria inside the mouth and preventing localized infections, which will heal in about two weeks. Hand, foot and mouth disease is caused by gastrointestinal viral infections. In addition to blisters in the mouth, blisters may also appear on the palms of the hands and feet. At this time, the child should be isolated, and the whole body supportive treatment, replenishment of body fluids, and appropriate amount of antiviral, antibiotic prophylaxis.