My 5-m.o. Baby keeps on gnawing. Is it a sign that a tooth is about to sprout?

Yes, gnawing/chewing behaviour is a common sign of teething. Other signs include: - irritability or fussiness - drooling (could lead to facial rash) - gum swelling and sensitivity - refusing food - sleep problems For more information on signs of teething: http://www.babycenter.com/0_teething-your-babys-first-teeth_11243.bc