For these symptoms, hives due to allergies and dermatographism and scabies bites are important possibilities to be ruled out. You can apply some calamine lotion at the rash
as it will help in soothing the skin
. You can take some OTC oral antihistamine medications like Benadryl or Claritin and see if it helps.
For mild-moderate symptoms a weak steroid may be used, whilst more severe cases require a higher-potency steroid.