There are several causes of a red genital area, but most infective causes usually cause itching and irritation as you rightly surmised in the question. Hence, fungal infections, bacterial infections and UTI seem less likely, but not impossible.
You should consider contact dermatitis
, allergy (most commonly due to bubble bath chemicals), or scratching as the likely causes. A mild steroid could easily reduce the rash within 4-5 days. Please ask the pharmacist for a locally available OTC cream of hydrocortisone
, both relatively mild steroids