"The sucking reflex is hardwired into the infant brain," Kundhardt says. "It's also among an infant's most soothing activities and an important way for her to release tension even after she's had her fill of milk."
Try this: Your baby's wails may simply be cries of hunger, so try nursing her or offering a bottle. If your child tends to get fussy after a meal, reflux may be what's bothering her. If so, feed her in an upright position and keep her that way for 15 to 20 minutes afterward. However, some babies have a need to suck even when they're not hungry; in this case, a pacifier can help.