My 15-month-old son has extremely irritated buttocks?

For a 15-month-old experiencing extreme diaper rash, the first step is to protect the skin with a zinc-based ointment at a concentration of 40% during each diaper change. Make sure to check the diaper often and change it as soon as it is soiled. If there is no improvement after 3-5 days, it would be advisable to consult with a pharmacist for alternative options.