Hello GaryC123,
Sorry to hear about your brother and this rash.
It certainly could be a drug reaction rash for which the mainstay of treatment is stopping the drugs.
Once these sort of blisters have formed there is nothing we can do to make them go away. They will eventually pop, but for preference should not be popped - the dead skin layer over the top of the fluid protects the sensitive layer below.
We do occasionally use steroids like Prednisolone 50mg daily for 3 days to get things to settle down.
Anyway, this should be treated like a partial thickness burn.
You can use an antiseptic cream, but only for 24 hours. All antiseptics delay healing.
All we really need to do is keep it clean AND not get it infected - it should heal rapidly with no scarring.
In a hospital environment, we would put a dry alginate dressing over the area and cover it with Hyperfix. This would be kept intact for about 3 days before looking at it again and redressing.
The low-tech approach would be clean well fitting cotton T-shirts changed every 24 hours . These would be likely to stick a bit but taking them off in the shower, not touching the area and letting it air dry before covering with a freshly laundered clean T shirt would do a reasonable job (in a pinch)