Hi thanks for writing here.Based on the description i would like to make following differential diagnosis.1.Since you both developed rash after stomach bug,it could be post viral exanthem
,it will subside by its own ,you can just apply calamine
lotion on it.2.If your child has received any medicines for stomach bug then rash could be drug induced,in that case stop drug,take anti allergic medicine,if rash still present then consult a doctor.3.Insect bite,many children are sensitive to insect bites
and it could also produce itchy rash,apply mild soothing lotion along with anti allergy tablets.4.scabies
,since you both have developed itchy rash there are chances it could be scabies,so it will be better you consult a dermatologist
who will help you cure your problem .