A rapidly spreading infection near the thigh and vaginal area for 10 days is most commonly due to a fungal infection like jock itch, especially in warm and sweaty areas where moisture gets trapped easily. It can cause redness, itching, burning, and spreading patches, and it often worsens if the area stays damp or if tight clothing is used. In some cases, bacterial irritation or mixed infection can also happen, so it is important not to ignore a fast spread. Keeping the area clean and completely dry is the first step that really helps. Loose cotton underwear, frequent change of clothes, and avoiding tight jeans can reduce friction and moisture. Medicated antifungal creams are usually needed to control such infections, but the exact choice and duration should be based on examination because groin infections can sometimes become stubborn or recurrent. Medicines/treatment should be taken only if advised or prescribed by your doctor. Avoid scratching, as it can spread infection further. If the redness is increasing quickly, there is severe pain, discharge, or no improvement within a few days, it is important to get a proper medical check-up to confirm the diagnosis and start correct treatment.