I have had a terrible rash ever since I started menopause about 2 years ago. Could it be related to the sweating in menopause?

Since your rash started with menopausal changes, it is probably linked to the changes in hormones associated with this stage of life. 

I would recommend Stinging Nettle from A.Vogel, a plant that helps strengthen the skin.  It brings a lot of nutritional elements necessary for a healthy skin, favours proper collagen levels and tissue healing.  Stinging Nettle also helps reduce the histamine production occurring in skin allergies.  It is particularly good with itchiness.

Make sure to drink a minimum of 2 liters of water a day.  Redness indicates some form of inflammation, which can easily dehydrate the body and make the situation worst.  Drinking a lot of water always helps with skin problems.  Make sure to include 1 tablespoon of cold pressed olive oil in your daily diet. You could also benefit from a good supplement of Omega 3.  Oils, taken on the inside, help moisturize the skin by keeping water in.  

Beware of the soaps that you use for your body and laundry.  Avoid perfumes since they can irritate the skin.  Chlorine can be a major nuisance if you are a swimmer or even from regular city water use.  In natural food stores, you can find showerheads adapters to dechlorinate water.