Thanks for your query
You seem to have developed a fungal infection
of the neck region which can be either tinea
infection or pityriasis
You should try to keep the groin region clean and dry .
Do not apply any kind of oils or moisturizing creams over the affected region.
You need to apply an antifungal cream over the affected area twice a day.
I prefer to use Clotrimazole
gel in such cases.
And to relieve the itching, take oral antifungals for long period .
Take oral antihistamines to relieve the associated itching.
You might need to see a local dermatologist
for confirmation of diagnosis.
Hope it helps ,
Dr Geetika Paul.