Seeing a derm about a rash that comes and goes

[PrettyCandles]

I'm seeing a derm soon, about a rash that comes and goes. When it flares up it is very bad indeed. Right now it's improving, and may well be almost healed by the time I'm seen. Which will mean a wasted appointment!

Should I stop treating it and let the rash get bad again, so that I present it in all its gruesome, flaking, glory and they can see the true extent of the problem?

I'd personally continue with the treatment unless it's in an area you can cover and/or it's not agony. I'd take lots of pictures of the rash as it is now, write down how it feels, record how it's changing/improving, ie: is it weeping etc etc. The same thing happened to me and the photos I took to my appointment really helped. HTH

Does it occur a few days after sun exposure, and only on those areas exposed to sun?

No, lostmymind. And I can find no triggers for it, it does not respond to anti-hitstamines, nor to dairy-exclusion or soya-exclusion (haven't tried wheat-exclusion). Creams make it vastly worse, and the only things that calm it are hydrocortisone and grease. Nizoral shampoo may be helping a bit. All I need to do is to stop greasing and it will flare up gruesomely.

I don't think so, and GP has not mentioned it.