The dam, which is usually brightly colored (blue or green), may alter the apparent color of the tooth, which can lead to incorrect choice of shade, e.g. during placement of a dental composite. For this reason, shades are normally chosen before the dam is applied. Latex allergy, depending upon the severity, may make the use of rubber dam uncomfortable afterwards (allergic contact dermatitis, allergic contact cheilitis, allergic contact stomatitis) or even life-threatening (anaphylaxis).