Oral rehydration salts (ORS) are mainly produces to treat diarrhoea in developing countries. They are supported by the WHO for treatment of diarrhoea http://www.who.int/maternal_child_adolescent/documents/fch_cah_06_1/en/. 

Unfortunately these kind of ORS are not available in some locations (in particular the UK) so they need to be ordered from abroad. There are other types of ORS available in the UK such as http://ors.uk.com/ or Dioralyte but I have tried them many times and they just do not have the same effect. I think it may be partly because they are only mixed with 300ml of water, rather than 1 litre but whatever the reason, they are not as good! ORS will not cure your hangover, but it will significantly reduce it. For example, if you’ve had a big night out and need to go to work in the morning, ORS will make that possible. It’ll still be a touch day and you’ll be tired, but it will be a hell of a lot better than without ORS – guaranteed! 

O.R.S is used by: 

• People who lose excess fluid 
• Professional and recreational athletes 
• Visitors to hot/tropical countries 
• People who work in hot climates