We are entering the seasons for winter colds and flu. Elderberry extract has been used for centuries to treat colds and flu. More recently researchers have found that chemicals in the berries may help reduce swelling in mucous membranes and relieve nasal congestion. Two different studies have shown that it also reduces the severity and duration of viral infections. Always check with your doctor before taking new medicines. Never eat raw, uncooked elderberries as it can cause nausea, vomiting, weakness and dizziness because the raw elderberries contain toxic compounds. However, the process of preparing elderberry extracts and concentrations removes those toxins.