Thank you for your query,
The itchy red rash involving creases looks like eczema or also called atopic dermatitis
The main stay in treatment is to maintain hydration, to decrease itching, and to prevent infection and trauma.
To maintain hydration apply emolient creams like dermadew or cetaphil
If there is severe itching
oral anthistamines like hydroxyzine
can be given orally in prescribed dosage.
Avoid allergic foods.
Consult the Pediatrcian to confirm and for the specific treatment.
Hope I have answered your query.