Ok, thanks for the added info.
There are several skin conditions that mock Jock Itch, but are not Jock Itch once looked at under a microscope. The best way to test for Jock Itch is to do a KOH test. This involves scraping the skin, adding the skin cells to a slide and then adding potassium hydroxide then the slide is heated. The slide is then viewed under the microscope to look for fungal elements specific for the Jock Itch virus.
My concern is that if this was not done, it might not be Jock Itch at all. Intertrigo is a yeast infection that occurs in the folds and cracks of the skin and can cause intense itching and even fissures (tiny cracks in the skin) that can lead to secondary infections. The other condition that mimics tinea cruris (or Jock Itch) is called Erythrasma. This is a bacterial infection that affects the groin (just as jock itch) and then it advances down the inner thigh similar to tinea cruris. However, the rash of erythrasma is flat and more brown than red throughout the affected area. It also does not have any scale or blisters.
I would HIGHLY recommend that you seek out a second opinion and see a different Dermatologist for a scraping and/or biopsy to see exactly what is going on so that you can be treated appropriately. IF you find out what is causing your itch, then yes, most likely there is something that will cure your itch once and for all.
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