Thrush. Thrush is a fungal infection that can form on the breast and be passed between your breast and the baby's mouth. Overly moist breasts, sore or cracked nipples, following a diet high in sugar or yeasty foods or taking antibiotics, birth control pills or steroids can all throw your body's natural yeast levels out of control and lead to thrush. Symptoms are very sore nipples, achy or painful breasts or pink, flaky, shiny, itchy or cracked nipples.

Your baby may have little white spots in her mouth, or a diaper rash that won't heal. You will need to treat both your breasts and the baby's mouth with a prescription antifungal or with the over-the-counter antifungal gentian violet. To prevent thrush, air-dry your nipples, use nipple pads in your bra, wear a clean bra every day, and reduce the amount of sugar and yeasty products in your diet.