The state of being easily affected or influenced by something.
Susceptivities can be good or bad, depending on what is affecting or influencing someone.
Examples:
Her susceptivities to pollen make her sneeze.
His susceptivities to cold weather make him wear a coat.
My susceptivities to scary movies make me cover my eyes.
The cat's susceptivities to catnip are funny to watch.
His susceptivities to tickling are so strong that he laughs uncontrollably.
The flower's susceptivities to sunlight make it grow.