HI, thanks for using healthcare magic
There are different causes for widespread rash, the most common is allergy. Other causes would be some types of infection but in that case there would be a fever
The most common cause of an allergic rash
at her age is food allergy
and I am assuming at 3 months she is presently only on milk with no additional foods or cereals added.
It is unusually for a child to have an allergic reaction
to nutriguiem milk because this is the milk used for children with allergies to dairy or soy proteins
In children eczema
can present in a wide spread fashion. This is a inflammation of the skin and is usually driven by some allergic stimulus as well.
If the rash is itching her, your doctor may suggest an antihistamine.
In addition , if he or she believes it is an allergy or eczema, she may be given a mild topical steroid
cream to apply. It would also be important to keep her skin moist, within 3 minutes of bathing a moisturising agent should be applied. It should be applied repeatedly during the day.
the source of the inflammatory response needs to be determined so it can be eliminated.
I hope this helps