Behavior Change in Loving Cat

Recently my 5 year old adopted cat has been aggressive to our cleaning lady/caretaker who has known him since he was adopted. I observed this behavior while home during her recent cleaning day. Bucky (my cat) was his normal sweet self until I left the room-then he hissed, growled and prepared to lunge at her. I did slap a newspaper on the ground which irritated him more. Once she left he was his normal loving self. We are due to be gone for a week where our cleaning lady will take care of him (she really loves him)and I am very concerned I do not understand-please any help would be appreciated.

Has she changed any of the cleaning supplies she uses maybe he is reacting to a smell. YOu might also want to have him checked out by for vet and run some blood work because there are diseases that can change a cats behavior.