Pharmacist explains why your cold and flu symptoms keep coming backAmir Bhogal says there can be seven reasons you can't shake an infectionView Image A man with cold or flu symptomsWhile many people assume lingering symptoms are part of the recovery process, recurring colds with symptoms that keep coming back can often point to underlying factors that are being overlooked, according to a pharmacist. When you're under sustained pressure, your body produces elevated levels of cortisol, a stress hormone that actively suppresses your immune response. Consistently getting at least 7 to 9 hours of uninterrupted sleep every night strengthens your immune response and supports recovery from infection. Meanwhile, zinc lozenges have shown promise in influencing cold symptoms and how long they last. Even moderate alcohol consumption can prolong cold symptoms or make them more likely to return once you start feeling better.