Babies Biting and Teething
My 10-month-old infant has started biting her sister. Is this normal? Could she be teething?
Unfortunately, yes. Infants explore their environment with their mouths. She may be teething at this age, and pressure on her teeth and gums can be soothing. Or it may be that your infant is communicating frustration with a situation in the best way she can, since her verbal skills are not well developed. It is important to let your infant know that biting her sister is not okay by telling her "no" and removing her from the situation.