Hi fledgling!
I have come to think the itching/pinch/stab is a last ditch effort by whatever "parasite" infestation to distress and toxify the host ............... especially when parasite cleansing , killing and d-worming................. In a social community where cross-communication takes place ............ if a colony is distressed it can signal the trigger of these irritations. Give the host something else to deal with/ think about.................... possibly to take the hosts attention away from whatever was harming the colony or just the more important ones............................