"Children of the night": Toddler bites his brother at bedtime

During a well-child visit, I found two bite marks on the back of an 18-month-old. Mom said the boy's 3-year-old brother bites him, usually when the boys are in bed at night (they share a room, with both in toddler beds). The biting happens only occasionally in her presence. When it does, she alternates between using time-outs and talking to the 3-year-old. I encouraged her to be more consistent with time-outs when she witnesses the aggression, but I am unsure how to advise her when the aggression happens after "lights out."

Martin Davis, MDMedford, Ore.

Biting is not an uncommon behavior in toddlers, although biting as the first disruptive behavior to occur after lights are turned out at bedtime does seem somewhat unusual. I assume that the size of the bite marks are consistent with the story that a 3-year-old bit the child and that there are no factors that suggest abuse.

The easiest way to address the night-time behavior is to separate the children or put the 18-month-old back in a crib so that the 3-year-old does not have access to bite him. However, the 3-year-old's behavior raises questions about other aspects of the bedtime routine. Is there a calming bedtime routine? Is the 3-year-old going to bed easily or is he resisting? Is there a consistent bedtime? Are there disruptive behaviors that the mother is ignoring that occur before the biting occurs?

Although I don't have enough information to know, I would be concerned that this nighttime biting is a marker for some other difficulty in the parent-child relationship. It seems unlikely that a tired 3-year-old who generally goes to bed easily after a calming bedtime routine would, without any warning or sign of distress, get up and bite his 18-month-old brother.

Nathan J. Blum, MD

DR. BLUM is associate professor of pediatrics, University of Pennsylvania School of Medicine and Children's Hospital of Philadelphia