In Drugs.com's Toxicology section on lavender, it states that the Food and Drug Administration has classified lavender as GRAS, or "generally recognized as safe," but that lavender oil has a low order of toxicity. Central nervous system depression has been seen in some who have taken too much lavender oil.
The University of Maryland Medical Center states that lavender has many medicinal uses such as for insomnia, agitation, alopecia and for aromatherapy. The scent has been known to help headaches, exhaustion and nervous disorders. The University of Maryland Medical Center also states that the oil should only be inhaled or used topically.