Dr. Brown s Natural Flow baby bottle was invented by a doctor and tested on his own children when they were babies, so you can rest assured that this product is as safe as it is effective. This revolutionary baby bottle features a patented no vacuum design. It helps colicky babies settle down/sleep and reduces colic, spit-up, burping and gas. This also helps to prevent fluid in the ear/no vacuum. It is easy to clean, and dishwasher safe.