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My wife had the same issues. I tried double cycle rinsing in the washing machine. That gave her relief. Then I knew it was the water or the soap not being rinsed good enough. Then I tried washing twice. Once with soap and the second without adding any soap. That gave 4 rinses. That helped even more.   We have hard water here. That's not good either. I installed a water softner to soften the water to get a better rinse. Now she doesn't have that problem any more. She had bump's under her bra strap from the soap mixing with her sweat. That's pretty well gone now too.   Besure your water softner isn't set to high. That'll add salt to. You can check that in the sink. Fill the sink with hot water and rinse out a wash rag. If you see suds in the water, you have it set to high.   Some laundry soaps are pretty harsh and don't rinse well.   Good luck. Do some experimenting on soaps and water hardness.