A Washington state woman is facing a first-degree child assault charge for allegedly putting bleach in her 14-month-old daughter's eyes, authorities say.

The case against Jennifer Lynn Mothershead, 29, of Buckley began in May 2011 when the daughter was airlifted to a hospital with a head injury. Doctors notified the Pierce County Sheriff's Department, suspecting abuse, and mentioned "some bruising and an eye infection that was concerning," court records state.

Antibiotics and eye drops were prescribed for the girl. Mothershead later said the girl's eyes were swollen shut and that the girl was "a fighter" when the drops were administered.

Police hospitalized the girl after placing her in state protective custody, and court records state a hospital staff member discovered a foul odor and eye-burning effect in the eye drops her mother had brought from home. Mothershead put bleach in her daughter's eyes over a two-month period, authorities allege.

Investigators worked on the case for a year, and a laboratory analysis of the eye drops by the Federal Drug Administration's forensic chemistry lab the Harborview Medical Center in Seattle indicated the presence of bleach, The (Tacoma) News-Tribune reported Tuesday.

Mothershead was arraigned Monday in Pierce County Superior Court on one count of first-degree child assault. Deputy Prosecutor Grant Blinn said he did not have information on a possible motive.