Bronchitis is caused by inflammation of the mucous membranes of the bronchi, the air passages that lead from the windpipe to the lungs. There are two main types of bronchitis, acute and chronic. Acute bronchitis often occurs during illness, most commonly viral infections, and goes away within a week or two. Chronic bronchitis is a more serious condition that develops over time. Symptoms may get better, but extended periods of inflammation lead to a build-up of mucous that can lead to long-term breathing difficulties. In either condition, an anti-inflammatory diet and the use of expectorants, agents that help clear mucous from the lungs, are the best course of action.