The most common bra style to lift and support breasts are Underwire bras. Running under the cup, underwires may be made of flexible wire, plastic-coated metal or molded plastic. The underwire is sewn between fabric layers and provides essential support as well as shaping. Underwire bras are so ubiquitous that they can be found in almost any style and fabric, including cotton.
Cotton is preferable to some women because of its softness and hypoallergenic properties. It's ideal for women with sensitive skin. Cotton also 'breathes,' which means it absorbs moisture and lets it evaporate--keeping you dry and cool. Although there are some 100% cotton underwire bras on the market, many will incorporate a small amount of spandex, elastane or some other modern fiber. This allows the bra to keep its shape and fit.