One useful anti-cancer drug can effectively erase the whorls and other characteristic marks that give people their distinctive fingerprints. Losing them could become troublesome. A case released online in a letter by Annals of Oncology indicates how big a problem of losing fingerprints is.

Eng-Huat Tan， a Singapore-based medical doctor describes a 62-year old man who has used capecitabine to treat his nasopharyngeal cancer. After three years on the drug, the patient decided to visit U.S. relatives last December. But he was stopped by U.S. customs officials for 4 hours after entering the country when those officials couldn't get fingerprints from the man. There were no distinctive swirly marks appearing from his index finger.

U.S. Customs has been fingerprinting incoming foreign visitors for years， Tan says. Their index fingers are printed and screened against digital files of the fingerprints of bad guys -terrorists and potential criminals that our federal guardians have been tasked with keeping out of the country. Unfortunately， for the Singapore travelers， one potential side effect of his drug treatment is a smoothing of the tissue on the finger pads. Hence, no fingerprints.

"It is uncertain when fingerprint loss will begin to take place in patients who are taking capecitabine" Tan points out. So he cautions any physicians who prescribe the drug to provide their patients with a doctor's note pointing out that their medicine may cause fingerprints to disappear.

Eventually， the Singapore traveler made it into the United States. I guess the name on his passport didn't raise any red flags8. But he's also now got the explanatory doctor's note -and won't leave home without it.

By the way， maybe the Food and Drug Administration， which approved use of the drug years ago， should consider updating its list of side effects associated with this medicine. The current list does note that patients may experience vomiting， stomach pain and some other side effects. But no where does it mention the potential for loss of fingerprints.