Alarms Active status is not changed, if I changed the Set points after active alarms

I am working on version 8.0 and I have setup the alarms many times and it is working OK initially then after if I changed the Set points after active alarms. It is not changing it’s status. e.g. if my Set point is 100 and PV crosses the 100, I am getting the alarm; to check the alarm, if I changed the Set point to 110; while PV is 105 which less then 110; still the alarm is showing active. It should be cleared. Could any one please explain?