Everyone! Friends, family, the whole world. Although officially after Reiki 1 you’re supposed only to treat friends and family. But where’s the boundary? Isn’t everybody a friend in a way? The difference lies in money matters. As soon as you charge for a treatment (even for family and friends), you’re running a business. And for that you need to have public liability insurance. But as long as you do it for free, you can treat anyone you like (unless, of course, they don’t want Reiki).
At least, this is what applies in the UK. In other countries, including a number of states in the USA, where each one seems to have a different law concerning complementary therapies, you may find stricter regulation. It’s best to check it out before you place your hands on anybody! Some states, for instance, require a Reiki practitioner to be a licensed sports masseur before they can give professional treatments. If in doubt, you can always play it safe: simply place your hands a few centimetres away from the body. As long as there’s no touch involved, there are no concerns. And there’s no difference in the effectiveness of the treatment either.