Thank you for your query on Healthcare Magic.
is mostly due to skin allergy
Do you have any history of food allergy?
If you find any allergen try to avoid the exposure to it.
For rash you can apply calamine
lotion externally for soothing effect.
Oral antihistamines like cetrizine
will give relief from itching.
Consult the doctor for examination of the rash and for prescriptionn of specific medication.
Hope I have answered your query.