I have to mix cornstarch with dr.smith's diaper cream, how should i store it?!

I have to mix cornstarch with dr.smith's diaper cream, how should i store it?

my son had a boil on his butt a week after he was born and the spot has never left. it's very close to his anus and his ped. has given me all sorts of remedies, some that work a little and others that just don't. this is our last option. if this doesn't work he'll have to get it surgically removed. =(
so, my question is how should i store it? my house is hot inside, we have window units in a few rooms but not in the baby's. so it gets hot in there and humid. is that an ok temp. to keep the mixture in? i have the mix in a baby food jar tightly sealed but by no means air tight. should i keep it by an air conditioner too keep it at a lower temp.? my concern is that with the cornstarch it might ferment or something like that with the heat. so what do you suggest i do?
thanks

I would keep it in the fridge...but you might want to go get some aloe vera and heal the boil...also if you take marajuana and soak the leaves in water and place them on the boil it will heal it...but since it is illegal...aloe vera will work to..get the gel and place it on the boil, it will draw the poisons out and heal the wound...it really works. Also tea tree oil is good but for that area it would sting to much...aloe is better...diaper cream and cornstarch are not going to heal it just make it a bit more comfortable...you might want to also think about giving him water...babies need water too and I have found that when babies have boils or sores that they do well when given water to clean up the problem...hope it helps