Welcome and thanks for posting your query to Healthcare Magic.
After reading your query thoroughly it appears the closest possibility of " Recurrent Vasculitis". This is a condition caused by inflammation of the small blood vessels in the skin.
This can be triggered by multiple factors including certain medications or infections and some times there are certain factors coming in day today life.
As the inflammation progresses it causes the kind of rash
which you mentioned. There can be multiple factors producing this condition which are included in day to day life and some times it is really difficult to find one exact cause.
As your problem is quite painful and distressing so it is better to consult a dermatologist
for best guidance.
For the time being you can follow the suggestions below:
-Apply over the counter calamine
lotion 3-4 times a day.
-You can do cold
water compresses to reduce the intensity of itching.
-Do not scratch or rub the skin as it can lead to further aggravation.
-You can take oral anti histamine
or levocetrizine under medial advise.
- For the pain part you can take any pain killer round the clock basis.
Hope these informations will help.
"With good health wishes"
Dr Sanjay Kumar Kanodia
MD (Dermatology & STDs)