From birth through the toddler years of wearing a diaper, your child can be at a higher risk for infections, especially a yeast infection. When your toddler develops a rash on his bum that does not go away after a few days of applying diaper rash creams or ointments, you may be dealing with a yeast infection.
Candida
Yeast infections that develop on your child's bottom are due to a fungus called Candida. This fungus is the same one that causes vaginal infections as well as thrush and thrives in a moist environment, which is why the infection can develop on the toddler's bottom, especially between the cheeks and closer to the anus. Candida almost always is present on both male and female skin; it just needs the right moist conditions to thrive and cause an infection. If your toddler has a current diaper rash or another condition causing sores or open skin on the bottom, this can provide a door for Candida to take hold.
Antibiotics
A yeast infection can occur more often when your toddler is on antibiotics or you are on antibiotics and breastfeeding, as the antibiotic can pass from your breast milk into your child. Antibiotics are meant to kill off bad bacteria, but they also can kill off the good bacteria that are responsible for preventing Candida from multiplying and causing yeast infections.
Thrush
If your toddler has had thrush, it can pass through the digestive system and create problems on your toddler's bottom as it passes out. Thrush is a Candida infection in the mouth that is common in toddler's, especially those with compromised immune systems. Since the same fungus is responsible for yeast infections, the fungus is transferable to other areas where there is the right environment to thrive.
Difference from Diaper Rash
While a yeast infection may develop from a diaper rash, the two skin conditions are quite different. You can tell a yeast infection from a diaper rash by the darker red color and slightly raised edge around the rash site. Yeast infections also last longer than a diaper rash and do not respond to typical ointments or powders developed for diaper rashes. Talk to your pediatrician about recommended treatment options if your child's rash is actually a yeast infection.


