The best way to prevent your child from getting diaper rash would be to keep their diaper area clean and dry as much as possible.
You should change the wet diapers at least every 2 to 3 hours and never go longer than 3 hours without changing your babies wet diaper otherwise they risk getting diaper rash and yeast infections.
Even if the diaper isn't completely full after 3 hours the diaper should still be changed.
Poop diapers should be changed as soon as you notice the baby or toddler has pooped in the diaper.
The bacteria in the poop can cause your child to break out with a bad diaper rash if your babies sensitive skin stays in contact with the poop for too long.
If your child has severe diaper rash your child's doctor will prescribe a stronger diaper rash cream called hydrocortisone cream which is much stronger than over the counter diaper rash cream.