Hello and welcome to health care magic.
The redness and itching are suggestive of an allergic reaction
to an irritant substance in your body wash. Or it can be an infection with common pathogens like trichomonas or candida. My advice is to visit an OBGYN
specialist and let her have a look. If it's due to trichomonas, she will give metronidazole
and anti histamine
If it's due to allergic reaction, you have to change your body wash again.
Even though the brands may change, the preservatives and anti perspirants may be the same;and allergy
to a single chemical can result in itching and redness. So make sure to go through the chemical composition as well during your next shopping.
Hope this discussion will be helpful to you. Thank you.