Synthetic comforters fill the need for consumers who want the look and flexibility of a comforter, but are allergic to down. In addition to being hypo-allergenic, synthetic comforters offer the added convenience of being machine washable. The sizes of most synthetic comforters are comparable to the sizes of down comforters so most duvet covers will fit properly. In climates where a down comforter might be too warm, a synthetic comforter offers a viable alternative.