In this study, we experimentally evaluated the hot carrier injection (HCI) degradation in Reconfigurable FETs (RFETs) processed on a 22 nm FDSOI technology, and identified the underlying mechanism. The HCI behavior in these devices differs from traditional MOSFETs: RFETs primarily show a threshold voltage (V_th) shift instead of the on-current (I_on) degradation typical in MOSFETs. In addition, the reversedbiased source Schottky junction in RFETs places the peak electric field at the source side, whereas in MOSFETs the highest field is near the drain. The source side degradation was confirmed by measuring transfer characteristics in both forward and reverse modes before and after hot-carrier stress. Furthermore, the V_th shift follows a power-law dependence on stress time, with a stress-voltage-dependent time exponent. These findings help in developing suitable degradation models and in understanding the aging effects of polymorphic circuits built from RFETs.