### instruction:
If you are a doctor, please answer the medical questions based on the patient's description.

### input:
Hi, my 1 year old baby began drinking whole milk on Dec 16th. Since then, she has not been sleeping well, her stool is white in color and she has developed a terrible diaper rash. Before whole milk she was drinking Similac Sensitive (lactose-free). Two days ago I switched her back to the Similac and her diaper rash has cleared and her stool color looks normal again. Do you think she is lactose intolerant? What milk should I feed her?

### output:

Hello, The lactose deficiency causing lactose intolerance may be primary that is since birth or may be acquired.  The acquired intolerance is following an episode of intestinal infection resulting in gastroenteritis.  The most common cause is rotavirus infection. This infection results in temporary lactose intolerance due to the resulting damage to the superficial intestinal lining of the intestines, the brush border cells, which produce an enzyme called lactase, needed to digest the lactose present in the milk.  The symptoms improve once the cell lining recovers. Did you breastfeed your child? If so and if your child was tolerating the breastfeeds then primary lactose deficiency is ruled out.  Why were you giving your baby lactose-free milk? Was that after an episode of loose stools?  A routine Stool examination with the presence of reducing substances will help in diagnosis. A breath test is also available.  However, it may not be possible to do in a small child. It is recommended that you keep your baby off all dietary products containing lactose for a period of 2-4 weeks and then gradually reintroduce them. Hope I have answered your query. Let me know if I can assist you further. Take care Chat Doctor. 