It seems that you may be having vasculitis.
Vasculitis is an inflammation of the blood vessels.
There are many causes of vasculitis.
Many times cause is not found.
You should be investigated for internal diseases.. Like allergy, infection, anaemia,DM,HIV and autoimmune disorders
and other diseases...etc
Bood tests like Hb,TC,DC,ESR,ANCA,CRP...etc may be done.
Steroids and other medicines..like aspirin,methotraxate, azathioprine
...etc to stop inflammation are often helpful.
For perfect diagnosis and treatment you must consult dermatologist
Dr. Ilyas Patel MD