Thanks for your query.
These kind of rashes are usually allergic in nature. Specially since it has responded to benadryl
. Did your daughter changed anything in her diet lately? At this age, most allergic reactions are related to food or milk. I suggest you keep giving her benadryl at the recommended dosage and observe her activity, sleep and eating. If you notice worsening, take her to the pediatrician
Have a nice day, and good luck.