I understand your concern.
It could be great if you could provide a photo of the rash
area to evaluate the changes myself.
Anyway, from what you are saying, it might be allergy
reaction to any new detergent or anything you might have applied/inhaled or consumed recently Fungal infection
is to consider to if no real allergen is found out.
For the moment, I advise to :
- keep good local hygiene
- apply cold compresses locally
- take antihistamines
If it won't get better, should consult further with dermatologist
for a more specific treatment.
Wish fast recovery.