Pediatricians say that bubbles and an irregular flow in a bottle can create a vacuum that forces fluids into your baby's delicate inner ear, possibly leading to ear infections. Dr. Brown's Natural Flow baby bottle features a patented internal vent that prevents vacuums. The unique natural-flow design also reduces the ingestion of air with milk or formula. And that means less discomfort for baby, like colic, spit-up, burping, and gas. Bottle is easy to clean and is dishwasher safe.