My 4 1/2 year old son has the same pimple-type bumPs on his bum/upper thighs for a week. About 20 bumps. He also has an anal rash which I'm pretty sure is caused by a fissure. He's had the fissure rash problem on and off for about a year. The bumps are new though. The post about mollescum contagiousum (warts) alarms me because he actually had those warts behind the knees, maybe 8 months ago, and i treated them aggressively but they've been gone for 5 months now. I hope it's not warts. I had to treat each wart with the little planter wart bandaids, cut in half, every day for weeks and it was a pain.
My son also is prone to rashes around his mouth this time of year, and as well he has bad heat rashes in the crooks of his arms right now. i really feel like he just has super sensitive skin/system and probably too much acid in his system and not enough water. I'm hydrating him, adjusting his diet, and i'm going to try the rash ointment/malox/oatmeal blend on his booty. I'm going to research the folliculitis and other big words i saw here too...
Finally, we took her to a different pediatrician and he said it is Folliculits. He prescribed Mupirocin and said to put a cap full of bleach in her bath. He also said that some kids/adults are more prone to it than others (he being a sufferer himself) and it may reoccur. He instructed us to use the cream and the bleach if it reoccurs.
Link to more info on Mupirocin
http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0000875/
I have so much experience with this. It first started showing up in my daughter at about 18 months. I mostly cloth diapered her up until then, but she got too big for them and I didn't think she would be in diapers much longer so I didnt buy the next larger size, chose to use regular diapers instead. She started with just one or two pimples and I wasn't worried. They started getting worse though and when i brought it up to the doctor she said since they didnt bother her we might as well leave it alone. I tried tons of diaper brands but never could find one that didnt bother her. They started getting bigger and more numerous so I finally took her to the doctor again a few months later. She told me it could be scabies. I really doubted that diagnosis since i am a stay at home mom and my kids really hardly left my side and no one at home had symptoms. She was really rude about it and i agreed to try the medication. It looked like it sort of helped but only for like the first 24 hours then it came right back. I got really paranoid and made the whole family get treated for it, isolated all the bedding and stuffed animals i couldnt wash for a week outside in below zero temperatures, and washed everything else in scalding water, ruining many sheets and the covers to my couch cushions. It didnt go away. I called her doctor and demanded to be referred to a dermatologist. The dermatologist said it was folliculitis and apologized that we had been put through the whole scabies ordeal. He gave me an antibiotic cream and that cleared it up. But it kept coming back because of the diapers so i finally got her potty trained. The overnight pull ups still caused the pimples to come back so we started a routine where i used alcohol based wipes that would kill the bacteria every morning. The pimples would come back every once in a while but only a few here and there. When she stopped wetting her pull up and slept in underwear the pinples totally cleared up. But she started bedwetting again when she started pre school, so back in the diaper, back to fighting pimples. There were only two brands of overnight pull up type diapers and both made her break out and she refused to wear cloth pull ups. But the reason i am posting now is because 3 weeks ago i discovered that CVS has an overnight pull up and guess what IT DOES NOT CAUSE PIMPLES. Her skin is covered in scars now but she has no more pimples, FINALLY. The other brands we tried were goodnignts and pull-ups overnights. I tried off-brands from walgreens and almost anyone else that carried off brand overnight pull up style diapers. cvs is literally the first brand i have tried that doesnt cause her problems. She will be 5 in a month, so it has been a long time fighting this. So my suggestion is to keep the area as clean as possible, do warm bleach baths if it is very bad (that was the dermo's suggestion), using over the counter neosporin helps, and cleaning them off with antibacterial wipes like wet ones or rubbing alcohol helps a lot too. If you have a cvs in your area (it is a pharmacy, for those who dont know), try their brand of pull up diapers. If you can, use cloth diapers or potty train because getting them out of the disposables completely will help the most. Dispisable diapers obviously cause pimples otherwise there wouldnt be entire internet discussions about it! Disposable diapers are horrible!