Enlarge / Chickenpox on a 1-year-old. (credit: BSIP/UIG Via Getty Images)

Thanks to the vaccination program that began in 1995, chickenpox is now relatively rare. Cases of the miserable, itchy condition have fallen more than 97 percent. But, while children have largely put the oatmeal baths and oven mitts behind them, doctors have apparently let their diagnostic skills get a little crusty.

According to a study published Thursday, public health researchers in Minnesota found that 55 percent of people diagnosed with chickenpox based on their symptoms were actually negative for the varicella-zoster virus, the virus that causes chickenpox. The study noted that the people were all diagnosed in person by health care providers in medical facilities. But, instead of chickenpox, lab testing showed that some of the patients were actually infected with an enterovirus, which can cause a rash, or the herpes simplex virus 1, which causes cold sores.

The study, published in the Centers for Disease Control and Prevention’s Morbidity and Mortality Weekly Report, supports expanding laboratory testing for suspected chickenpox cases in the state’s program and highlights that diagnoses based on symptoms are “unreliable.”