My son used to get terrible diaper rash and I tried absolutely everything in the diapering aisle, it seemed. Then I remembered something we used at the hospital (I used to be a pediatric nurse) when babies had bad diaper rash. It is called Resinol. Its actual use is for burns or skin irritations. I've only found it once actually out in an aisle, at Target. Most of the time you'll have to find it behind  the pharmacy counter or the pharmacist will have to order it for you. It is over the counter, so you don't have to have a prescription. This stuff is amazing. It usually clears up diaper rash in a day or two. Just apply it to the bottom of your baby 2-4 times a day. When you change your baby, if there is still some Resinol on his or her bottom, don't wipe it completely off, it will just irritate the bottom more. It is the only diaper cream I keep in the house now. My second son has never had a diaper rash. As soon as there is even a hint or pink, I put this stuff on and he's better by the next diaper change.