Any sexual activity? What has your genital skin been in contact with? Anything different in terms of using a soap, shower gel. other body wash, even soap powder or fabric conditioner you may not have used before can cause this.
Most common issue is fungal type infections - this time of year we are spending more time in heated environments with heating on such as at home or at work, as a result we sweat more and this creates a breeding ground for naturally present fungi or even bacteria to get out of control and cause issues like this.