We report on the development of a microfluidic system for the electrical detection of single pollen allergen particles. Our device consists of 500 nm electrode gaps fabricated in an 800 nm wide fluidic channel. We flowed pollen allergen particles of average size 330 nm along the channel via fluid pumping and simultaneously monitored temporal change in dc current flowing through the sensing electrodes. Current spikes were detected, which can be attributed to a capacitance discharging upon trapping/detrapping of single allergens in the electrode gap. This sensing mechanism may open new avenues for a highly sensitive pollen allergen sensor.