A diffuser attachment is designed to disperse the air flow of a blow dryer and spread it over a larger area. Diffusers are used principally with curly hair because the dispersed air doesn't disturb the hair's wave pattern or cause frizz when drying. There are several diffuser designs: flat vented and mitt diffusers, as well as finger diffusers that lift hair, adding body while maintaining curl or wave without frizz. All diffusers should be used with a dryer set on low speed and heat settings. Using a diffuser with a dryer set on high defeats its purpose and can cause the dryer to overheat. Keep the dryer moving. Never let the air stay directed at the same spot for any length of time.