I would for sure be talking to your Dr directly on this one especially if you have alergies... pregnancy can make you more sensitive and it could be scary if you were to get some bad advice... you could always talk to the pharmacist as well as they are the experts :)
i broke out into a terrible rash on my belly around like 26 weeks and went to my dr and they said it was like diaper rash just from the heat and my maternity pants covering up that skin so it can't breath. he suggested desitin or some kind of baby diaper rash cream. you should definitely talk to your dr though because it can be PUPPP, google it it looks miserable I was terrified I had it, luckily i didn't!