could be psoriasis, but more likely to be candida... gf need not be suffering from thrush for you to have it.
Canesten or nystatin will clear it up
Hello,
The exact cause can be determined only after a complete medical history and clinical examination. It can be due to dermatitis, sweat dermatitis skin or balanoposthitis .In Balanoposthitis there is inflammation of the glans penis.This can occur due to collection of smegma and lack of hygiene. Topical antibiotics, mild steroids may be needed depending on the severity of infection. You can apply some calamine lotion at the rash as it will help in soothing the skin. Also wear cotton undergarments. If the symptoms are severe then it will be best to consult a dermatologist.
I hope it helps. Take care and regards.
Best of luck and regards!