The weather. As the weather gets colder and we turn on our heat, our skin drys. Your breast tissue is doing the same thing, but when you release the suction, it cracks the dry skin, causing the tinest drops of blood. Now, what to do about the milk, my pediatrician said, that since it only happnens at the end and none is getting into the milk, the milk is fine, and that the tinest amount of blood in the milk will change the color to a pink tint, if that happens, throw the milk out, otherwise it's good. Now, of course whatever is in your blood is in the milk anyway, but once it comes in contact with the outer skin, it can bring the bacteria that normally is on your skin into the milk, while it wouldn't get in on any other occasion. I used lanolin after each pumping and if it got bad, before, because it prevents the blood from getting out, just put small dabs around the areas that are red and away from the nipple. Then if you're not nursing or if you can go all night without nursing (if your baby sleeps through the night) put some heavy duty, non-scented lotion on your breast to help with the dryness, just wipe them clean before you pump/nurse. This worked wonders for me and I hope it does for you too. Merry Christmas!!