Hi welcome to Health care magic forum. As your description suggests that the pus filled boils
are coming on upper arm, chin and back, recurring and at the same spots, leaving red scars
. It appears to be due to infection of the hair follicles, not treated completely.
As they are troubling you since long it will be advisible to have a culture and sensitivity of the pus of the boils, besides other routine tests for confermation of the organism present in pus and the antibiotic which is sensitive to the organism.
Besides i advise you to avoid body sprays and powders, and maintain good hygene .
I also advise you to avoid pulses, potato and other tubers, and fish, to avoid pus formation in presence of infection.
Wishing for a quick ad complete recovery and thanks for calling.