This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Pediatrics
A baby presents with diarrhea and perianal diaper area redness. Diagnosis is 
Select and explain. 
A. Lactose intolerance, B. Shigella diarrhea, C. Salmonella, D. Fungal
A: Lactose intolerance
Answer: A: Lactose intolerance 
Explanation: In Lactose intolerance, there is a deficiency of the enzyme lactaseSo there is no natural breakdown of lactose - a carbohydrate present in milkThis causes diarrheaThe stool contains reducing sugar which causes perianal excoriation(Refer: Nelson's Textbook of Pediatrics, SAE, 1st edition, pg no. 1876)