Ammonium Hydroxide and Ammonia are identified as food additives that may be safely used following prescribed conditions.
Link to FDA Code of Federal Regulations
http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRS...
http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRS...
http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRS...

Ammonia has been evaluated by the Agency for Toxic Substance and Disease Registry, which is part of the Centers for Disease Control and a toxicology fact sheet is available at
http://www.atsdr.cdc.gov/tfacts126.pdf

Ammonia is listed in the Cosmetics Directive of the European Union (see Annex III, Part I). It is allowed for use at a maximum concentration of 6% as NH₃, and must be labeled, contains Ammonia if the concentration is above 2%.
Link to the EU Cosmetics Directive: http://ec.europa.eu/consumers/sectors/cosmetics/documents/di...

Ammonia used commercially can be anhydrous ammonia (not dissolved in water) or an aqueous solution of ammonia and water referred to as Ammonium Hydroxide. Anhydrous ammonia must be stored under pressure or at low temperature to remain a liquid.