What would cause your urine to burn the skin?

http://www.mothernature.com/Library/Bookshelf/Books/16/246.cfm

http://www.ic-network.com/handbook/selfhelp1002.html

I am not a physician (yet), but I would assume urine would burn the
skin because it is too acidic.  Acidic urine can be the result of many
physiological disorders (improper kidney function, high blood gas
levels of carbon dioxide, etc.), so it is therefore important to
contact your physician to determine the source of the problem, as
several tests would likely need to be performed.  Of course, there
could also be an entirely different reason... some sort of skin
disorder could be involved.  Again, no one cause can be pinned down
without seeing a physician.

You need to have a doctor do a urinalysis to make sure you don't have
a urinary tract infection (UTI).  If you do and it's untreated, it may
spread up to your kidneys and cause an infection there
(pyelonephritis).  There are other possible causes of burning with
urination, so your doctor should evaluate you.