Did you know that your body stores mucus. So anytime you detox and OP is a form of detoxing, you will remove some stored mucus. Eating Sugar and processed food causes the body to make mucus. If your lymph system can't remove it fast enough it will be stored. Mucus can be stored for years.
Several years ago I did a complete detox along with a diet change and I still can't believe how much better I can breathe.