• N-Acetyl-L-Cysteine (NAC) - helps reduce inflammation of bronchial tubes and lung tissue, loosens & thins mucus.
• Zinc - Helps fight infections (helps produce activate T-Cells to fight infections) and reduces symptoms by a day or so. (Taking 150mgs a day or more can result in zinc toxicity, be aware.)
• Vitamin C - Supports your immune system, also helps with iron absorption.
• Echinacea - increases the number of white blood cells to help fight infections.
• Elderberry - Good source of antioxidants; specifically, phenolic acid which helps to reduce oxidative stress damage, as well as flavonol antioxidants quercetin (reduces inflammation, lowers blood pressure, relieves allergies and sinus issues, amongst other benefits), kaempferol (fights free radicals, reduces chances of cancer, prevents oxidative damage) , and isorhamnetin (improved heart health and reduces inflammation).
• Vitamin D - Helps body absorb calcium and phosphorus, helps prevent respiratory infection, could also be therapeutic for autoimmune disorders.

None of these are cure alls, but do what you can to prevent and/or reduce potential damage now so if you get sick later, your body isn't fighting it without the proper tools.

• Hydration is also important. Getting enough water is essential to EVERY function in your body. In this case, it helps to keep mucus thin and cuts down on congestion.