In this work, oxidation processes are correlated with the current-voltage characteristics of few-layer black phosphorus obtained by liquid-phase exfoliation. Black phosphorous (BP), a room-temperature p-type semiconductor, exhibits an anomalous switching behavior between 373 and 448 K. The anomalous increase in electrical resistance is explained using a combined spectroscopic and DFT approach. The activation energy for thermally activated electrical conductance was calculated from the current-voltage characteristics and correlated with the oxidation processes. The activation energy for thermally activated electrical conductance in the dangling oxide BP phase was found to be 79.7 meV, ∼40 times lower than that in the interstitial counterpart. First-principles calculations reveal electronic differences between dangling and interstitial oxides, and electrical resistance measurements reveal a Schottky-to-ohmic contact formation related to the differences in the calculated work function of dangling and interstitial oxides. We propose that this phenomenon can be exploited as a fast, economical method for the evaluation of the oxidation processes in few-layer BP.