This syndrome is temporary and results from the decreased output of the sympathetic nervous system to your brain, face, head, neck, arms, and chest.  It causes a slight droopiness of the eye, redness in the white of the eye, a smaller pupil compared to the unblocked side, a stuffy nose on one side, and flushing of the eye, face, neck, ear, shoulder or arm.  The skin in these areas increases in temperature around 1 degree Celsius and appears flushed or red.  It is not necessary to see all of these, but I prefer to see at least 3 different signs to indicate that we did a good and solid sympathetic block.