Hello, How long has she had this? Is she otherwise healthy? The most common cause is an accumulation of dust, cotton fibers from clothes, dried perspiration, and dirt. Try wiping it out of her belly button using a moist cotton swab. Followed by a bath in tub paying particular attention to wipe out belly button with a wet washcloth. When it is all cleaned out, watch it frequently(every 2-3 hrs) to see whether any drainage reappears. Should you see more drainage, then she probably ought to be seen by her primary care provider because rarely there can be a small tube-like connection between the intestine and belly button through which fluid from intestine drains. Hope I have answered your query. Let me know if I can assist you further. Regards, Dr. Arnold Zedd