I am not sure about the diagnosis here as hives do not usually affect the bottom.Also the hives rash usually only lasts for a few days not 2 weeks.Try him on an antihistamine such as Allecet syrup 5ml once daily [at bedtime] and if the rash does not clear after 3 days your son should be seen by a doctor even if you have to take him to the paediatric department of your nearest public hospital.
The information provided does not constitute a diagnosis of your condition. You should consult a medical practitioner or other appropriate health care professional for a physical exmanication, diagnosis and formal
advice. Health24 and the expert accept no responsibility or liability for any damage or personal harm you may suffer resulting from making use of this content.