Hi, welcome to the forum, her symptoms are suggestive of diaper rash a type of irritant dermatitis. It seems secondary to the garments or diaper she is wearing and sweating will worsen the condition. If it is left untreated for more than 3 days then it can lead to Candida (fungal) infection. That may cause smell and discharge.
Firstly, she should be taken for investigations as it should not spread and worsen. The affected skin scrapping can be subjected to KOH preparation and microscopy to confirm fungal infection. Otherwise it strongly suggests irritant dermatitis.
- White petrolatum, Zinc oxide cream or Sucralfate can be used which acts as protective barrier.
- Use of powders such as cornstarch or talcum powder is also helpful.
- Topical Antifungal agents such as clotrimazole or miconazole against prescription is quite useful to check fungal infection and hastens recovery.
- Low potency glucocorticoids can be helpful.
I suggest you to consult dermatologist. Take care and regards.
This could be a yeast infection or even heat rash. Make sure that her pants are not tight and rubbing up against her. Try feeding her yogurt which will help if it is a yeast infection. Make sure that she is wiping from front to back and cleaning well, because sometimes this can cause irritation. Also make sure that after baths, she is completely dry before getting dressed. You can get corn starch and place in her pants to help with chafing. Hopefully this will help, but if the problem persists, I would take her to the doctor to make sure that this is not something more serious.