Lab swabs are typically composed of a narrow shaft with a swatch of foam, cotton, rayon, or polyester on one end. The shaft may be made of paper, wood, or plastic such as polypropylene. Lab swabs are available in varying lengths suited to their specific application. Foam swabs or large cotton swabs are commonly used in medical, dental, or scientific research settings. Medical personnel may use a cotton-tipped applicator to clean a wound or apply topical medicine. Lab swabs are commonly used to collect cells from the mouth or throat for diagnostic tests or DNA testing. Sterile swabs help prevent contamination of samples or the area to be swabbed. Dental swabs are used to apply bleach during teeth whitening processes. Foam swabs are often used to clean sensitive equipment with narrow spaces such as copy machines, printers, and electronics.