10 minutes ago, KennethT said:@liuzhou Is lettuce easily available where you are?
Yes, every market, supermarket and restaurant has it, although the locals usually cook it. As do I sometimes.
10 minutes ago, KennethT said:What do you wash it with?
Tap water.
The local water is fine. At least, I've never had a problem with it. I don't drink it, though. Some people (not locals) use bleach solutions or sterilising kits designed for babies' milk bottles. Totally unnecessary. But I'm just talking about where I am.
As you say, Vietnam (and other SE Asian countries) do eat raw vegetation and happily wash it in the local public supply.
In 22 years in China, the only time I got food poisoning was in a Western restaurant in Xi'an.