Have a reoccurring irritation on pubic hair area of my vulva. It looks a lot like razor burn, but seems to occur when wearing synthetic undergarments. Occasionally I'll get a flare up before my period. The same thing will happen on my breasts when wearing a bra with microfiber lining. What it seems like is that my skin isn't staying breathing enough in these instances, and if the area on my vulva is shaved, the small bumps are more likely to go away quickly. Does this seem like it is hormonal, diet related or due to an underlying infection?

You could be sensitive to synthetics. The best way to find out is to get a pair of cotton lined panties and wear only that type. You'll find out soon enough that is the case. Bras are also in a hot area of the body and this could also be the problem there as well. Cotton bras are not glamorous to say the least but at least you won't have the rash there either.