A three-year-old child’s back is full of small bumps is usually associated with papular urticaria, eczema, prickly heat and other conditions. 1. Pemphigus urticaria: If a three-year-old child’s living environment is humid, mosquitoes are more, it may lead to the occurrence of pemphigus urticaria, which usually manifests itself as a symptom of the back is full of small bumps. 2. Eczema: If a three-year-old child suffers from eczema, it may also lead to a back full of small bumps, usually accompanied by itching and other symptoms. 3. Prickly heat: If a three-year-old child sweats a lot in a hot and stuffy environment and doesn’t get rid of it in a timely manner, prickly heat may be formed, manifesting itself in the form of small bumps on the back. The three-year-old child’s back is full of small bumps, there may be other reasons, it is recommended to go to the hospital in time to improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.