While most people have no problem using condoms and wearing latex gloves a small percentage of the population is sensitive to natural latex rubber. It is a potentially life threatening condition and symptoms can range from minor skin irritation to anaphylactic shock. One section of a device used for barium enema procedures had to be recalled because people where dying from the severe latex allergies from its inflatible latex tip. One big problem is that latex is a component of many medical devices including but not limited to surgical and examination gloves, catheters, condoms, dental dams, intubation tubes, anaesthesia masks as well as enema tips. The primary source of allergic reaction appears to be proteins in the latex itself.
info from www.hc-sc.gc.ca as well as the Canadian Latex Allergy Association