You see no improvement after four days of home treatment or anytime it seems to be getting worse rather than better. It's possible your child may have developed a strep or staph infection or a local reaction to a particular lotion, soap, or laundry detergent.
The rash is scaly and has a yellowish hue and appears not only in the diaper area but elsewhere on the body, such as behind the ears or under the arms. Your child may have seborrheic dermatitis.
The diaper area is covered with blisters that leave shallow red sores. Your child may have impetigo, which requires treatment with antibiotics.
Your son's penis is swollen and red and you can't retract the foreskin, or you notice a greenish discharge from the penis. Your child may have a painful condition called balanitis, which requires antibiotics.