A trial has begun in Orange County in the case of a mother who alleges her 7-year old daughter died from a fatal reaction to treatments for cerebral palsy using the blockbuster drug Botox.

It is believed to be the first case alleging a fatal reaction to Botox to reach trial.

Federal authorities last year mandated "black box" labels that warn of potentially serious reactions to Botox.

While the drug is known for cosmetic uses, it has also been prescribed at doctors' discretion to relax muscles in cerebral palsy patients.

Kristen Spears died in November 2007 of respiratory failure and pneumonia. Her mother Dee alleges an overdose of Botox weakened muscles that controlled her breathing.

Irvine, Calif.-based drugmaker Allergan Inc. declined to comment on the trial.