Thanks for writing in.
The condition you are suffering from can be drug rash,urticaria,contact dermatitis
Penicillin can give rise to rash as described by you.
Proper examination KOH scraping,patch testing,skin biopsy
may be required for diagnosis.
is a steroid and long term intake is not advisable.
Consider visiting your GP or dermatologist
for proper diagnosis and treatment.
You can take tab.Zyrtec for itching till you visit a doctor. Also you can apply soothing Calamine lotion over the affected area.
Hope this helps.