Hi i have a girl 5 years old and she have a bag smelly underarm ss is normal that at this years she get that bad smelly please let me now thanks ?

Sweat: I assume her smelly underarms come from her sweat smelling that way. If she is, otherwise, healthy, i would not worry about her sweat smelling that way. It is genetically set and hormone regulated. It may change with time especially when she goes through the periods of hormonal changes. It may become more or less smelly. If she has other symptoms or is not doing well, otherwise, consult her doc.

A little unusual: Her smell probably falls within the normal variation that children of this age have. Rarer causes of new onset body odor in the young can involve entering puberty too early. This is usually accompanied by other changes such as pubic hair or even voice changes. If she has any other symptoms, she should be seen sooner than later, otherwise i would bring it up at her next visit.