Tell me about a child's language in ulcers and how can we explain the …

Tell me about a child's language in ulcers and how can we explain the burns inside their lips? We thought it might be an allergy, but I don't think they ate anything unusual. In the village, we went to the hospital, but it was useless. They took a swab and sent it off, and there was silence. Could anyone have experienced this before? We can't understand what is causing it. It's not my child.