The nurse is concerned with the prevention of communicable disease primary prevention results from

D. give an antipruritic medication such as diphenhydramine (Benadryl).

Antipruritic medicines such as diphenhydramine are useful for severe itching, which interferes with sleep and may contribute to secondary infection.
Cool baths, not warm ones, are recommended for relief of itching secondary to chickenpox.
Neither drug provides antipruritic effects, nor should aspirin ever be given to children with chickenpox, because there is an increased risk of developing Reye syndrome.