I got it when pregnant with the twins and it was excruitiating, my Ob prescribed me topical steriod cream to help reduce the itching but it never took is away. All I wanted to do was scratch all the time, which was heaven but did leave me red and at times bleeding. I used to sleep with my belly exposed to the open air as having any covers over me would just increase the itching.
Unfortunately the only guaranteed relief is for the baby to be born and they say it should go away in about a week. For me however PUPPS started around 26 weeks and I still had the rash 8 weeks post delivery (my stomach was a big red lumpy rash especially in my stretch marks), but they say PUPPS is more prone in pregnancies when you are having a boy due to the increase in testosterone in our bloodstream (which is too high for us to handle) and seeing I was carrying 2 boys it took longer for the testosterone level to decrease in my body post delivery.
I feel your pain and hope you can make it through the next few weeks, and I'm tipping you have a little man in there causing these issues
For instant relief, I would use cold face washers on my belly, pinetarsol (smells but helps for a little while), pawpaw ointment. Basically anything that will help cool and sooth the rash.
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