After a scrape 7 days ago, & putting a plaster and betadine/iodine paint, i developed a red, blistering rash.doc gave betamethasone but its not working?

Possible allergy: Betadine and other iodine-containing topical treatments can be very irritating to the skin, and in some cases can cause tissue damage. An allergic reaction to iodine is also possible. All can take time to calm down, even with a decent topical steroid. I often recommend a simple route by using plain vaseline on a superficial wound to protect while your body does what it does best to heal.