Anyone experienced this?

 As per normal ice had a few rash spots on my sides, back the ones you swear your going to scratch through your skin itchy!  But tonight as I was changing my husband noticed my entire right backside from top to buttocks is very bright red splotchy rash, only it disentangle appear to be on top of the skin, you can't feel it, it's not itchy, but very large area.....

Anyone had this? 

nope and I would suggest that you see a doctor.

Are you on any  new meds?  Could be an allergic reaction...That happens to me when I take codiene.

Have it checked out!

Your skin throws off dead cells every day. With rapid weight loss it cannot keep up and a layer of itchy skin develops. Get a doctor to check out the rash but exfoliating will probably do the trick.

Using creams will make it worse. Get the dead cells off and the itching will go away.