We don't know yet. There is no conclusive research yet on these products. Plugged (or clogged) ducts are unlikely if you breastfeed often to keep your breasts soft and comfortable. If you're using a stick on product like SimplyLily LilyPadz (silicone nursing pads), make sure to clean them with white vinegar and water to keep them sanitary. Using soap ruins their ability to stick to the breast.