Lara has great advice.

I get it too—antibacterial soap is the worst. Washing with dandruff shampoo (I use generic Head and Shoulders) and putting antifungal cream on it helps (I use generic lotramin).

Only use soap where you have to. You don’t need to soap every square inch of your body.

If that doesn’t work, try looking into dietary causes. The Paleo diet might help (meat, veg, fruit diet) that eliminates suspect foods. There is an elimination diet I’ve heard of, but I haven’t tried it.