I Have A Resident With Severe Itching Of The Skin

I have a resident with severe itching of the skin with a scattered thick red rash on approximately 80 % of her body. The itching is not bad during the day but gets extremely bad starting about 5 pm and continues throughout the night. The Vistaril that is ordered is 25mg Q 4h and is not totally effective and the itching gets increasingly bad after about 3 hours?