An apparatus for modifying a keratinous surface that has a rotatable applicator that is in fluid communication with a first modification composition. The apparatus also has a sensor and a CPU. The sensor is positioned forward of the applicator head such that as the head rolls across the keratinous surface the sensor reads the portion of the keratinous surface in front of the rolling head. The sensor readings are transmitted to the CPU, the CPU analyzes the sensor readings of the keratinous surface, and the CPU sends a signal to the applicator head to treat or not to treat the analyzed surface. When the CPU sends a signal to the applicator to treat the surface, a small portion of the first modification composition is applied to the head such that when the head rolls over the keratinous surface the first modification composition contacts the area of the keratinous surface that needs treatment.