Underwear area rash - please help

[CaptainEll123]

Hey everyone,

I've had this recurring rash over the past year or so and I've tried everything to narrow it down short of visiting a dermatologist (who locally have a 3 month waiting list) so in the meantime I would really appreciate some help. Here is the down low:

- I live in coastal Australia so its always hot and humid here
SITE
- Starts at belt line and moves down to upper thigh. Nothing in actual groin area or on genitals.
- Only appears on anterior aspect of the body.
ONSET
- Starts off as a light salmon/pink rash and progresses to the state it is in the picture i provided. From here it usually lasts a week or so before disappearing.
- Notice it after a day at work or school and commonly occurs after exercise
CHARACTER
- Small spink/salmon bumps and sometimes small plaques
- Non itchy - There is no sensation associated with it. I can never tell if i have it until i look
RELIEVING FACTORS
- Earlier the only thing that has helped has been soaking in the ocean for ~30 minutes. But lately, this has proven ineffective. When it did work, it would help the rash calm down within a couple of days instead of the usual week.
EXACERBATING FACTORS
- Heat and exercise seem to make it spread more rapidly and delay its dissipation
TIME SCALE
- Started about a year ago since we moved up here from a colder climate
- Lasts for about a week or slightly longer
PREVIOUS FINDINGS
- Non fungal (had skin scrapings and culture performed last time I had it)
    - Previously did not respond to Hydrozole or Daktarin
- No response to Bactorban (thought it may have been associated with bacterial infection) but there are never any pustules or discharge
- No response to topical corticosteroids (Diprosone)
ATTEMPTED REMEDIES (Ineffective)
- I have changed underwear to only cotton and white (non-dyed)
- I have changed to sensitive laundry detergent, with cold wash and an extra rinse cycle
- I have been having only cold showers for the past 6 months
- I try to shower right after any sweating or exercise
- I use unscented crystal deodorant
- I use QV sensitive body wash (Australian soap,fragrance,etc free wash)

So there it is. To me it seems like some sort of heat rash or sweating problem but it only appears in this area and I can never pinpoint the reason. Sometimes I will sweat heaps and nothing then a few days later, after a full day in air con it will be there when i get home. I would sincerely appreciate help with this and am happy to answer any additional questions that may help get to the bottom of this.

Regards