I will apologize upfront for the length of this, but unfortunately I have alot of experience in this area!
Corona cream (find at feed stores or online). You've heard this already, but here's more info on it. It's an animal ointment, but don't let that scare you off. Here's why...my close friend had a toddler in Tx. Children's undergoing chemo treatments for leukemia. They could not give him anything that was not approved by his doctors. When nothing prescribed worked for his chemo-induced rashes, the doctors agreed to have the pharmacist test the Corona. The pharmacist approved it, saying that it was far superior to anything he could prescribe. It kills bacteria and fungus.
I used it on my baby, and it was a lifesaver. No more fire-red, bloody rashes. Instant soother.
My baby had problems with rashes and allergies after I stopped breast-feeding him at 8 mos. old. I, too, went to cloth diapers (Fuzzi Bunz are what I use). They helped tremendously! I use cloth baby wipes, with a natural cleaning solution containing tea tree oil and lavender. I found both at www.nurturedfamily.com.
My son is now 2 years old. He appeared to me to get rashes and/or congestion every time I fed him particular foods. The rash would start off as dots on his skin, from the diaper area and sometimes all the way up to his neck, and then worsen to the red skin with dots in the diaper area, which is typical of a yeast infection. I believed the entire rash cycle was starting with food allergies. So, I had him tested for allergies, using NAET, an alternative approach. You can google it to learn about it. We had great success treating his allergies(which were just about everything he ate, chemicals, airborne allergies, etc) with NAET. It sounds very weird, my husband thought I was nuts, but it worked and now my hubby thinks I'm a weird genius.
Since using the cloth diapers, Corona, and doing the NAET, I have tried disposable diapers on a few occasions when I forgot to wash diapers. Here's what I found: non-chlorine diapers are fine for my child. I find them at Whole Food and online. Any regular disposable diaper other than non-chlorinated turns his bottom fire-engine red in an hour or less. What's worse than the diapers, though, are the baby wipes. He screams within a minute of a conventional baby wipe touching his skin. The disposable wipes that I can use on him are the 1st Generation non-chlorine wipes, and Lansinoh brand wipes for breast-fed babies.
A few words of caution about cloth diapers and any cream you put on the skin: Do not use cream and then place a cloth diaper directly on it. Use a liner that will touch the cream instead of the diaper touching the cream. Wash the liners completely separate from the diapers. Not using the liners, or washing them together w/ the diapers forms a shield on the diaper that causes them to wick the moisture away, therefore making the diaper leak instead of absorb the fluid. Also, if you use fabric softener, either liquid in the wash or sheets in the dryer, you will get a coating on the dryer which will then be transferred onto the diapers, which will form a film on the diaper that causes the moisture to wick away from the diaper, therefore causing leaking.
Next, colloidal silver. Get at Whole Foods, or other health food stores. Get a minimum of 50ppm (the strength), and be sure it is in a dark glass bottle. If there is bacterial infection, this will clear it up, without harmful antibiotics that will just increase the yeast infection rash. Yeast and bacterial infections in a rash often go together. Just use a cotton ball, pouring the colloidal silver on the cotton ball and dabbing lightly on the skin.
Give lots of probiotics, like acidopholus and bi-fidopholus. Again, find at Whole Foods or other health food stores. Be sure they are refrigerated, as this helps them to last longer and be higher in number. You can find them in liquid, powder, or capsules. Easy to put in a bottle, applesauce, yogurt, etc. Probiotics are beneficial bacteria that are naturally present in the digestive system. When they are killed off by antibiotics, the fungal (yeast) growth gets out of control and you see yeast infections. Yeast infections show up in your typical yeast problems in females, but also in diaper rash, itchy ears, thrush in the mouth, "heat" rashes, etc. They can literally go super-crazy causing unbelievable issues like infertility in the long-term.
If you don't have complete success with the above, look into all-natural, organic body products for bath soap/gel, shampoo, lotion, etc. Whole Foods carries several brands. For us, the brand that I like the best is California Baby. They carry everything from a great shampoo/body wash, to sunscreen, bug spray, etc. It it more expensive than what you can buy at Target or WalMart, but if you're still having any issues with rashes, the parents won't care about the higher price for skin products! Whatever you do, check www.cosmeticdatabase.com to find info. on the toxicity of the ingredients for each product. California Baby products rate extremely well!
Best of luck to you all! I wish you the best, and hope you find a solution quickly.