Cultural and public health observations in Vietnam

Without judgement, some observation notes for safekeeping: 

1) stark emphasis on age rank, almost opposite the US. Instead of how are you, the polite thing to ask upon first meeting someone is their age

2) people don't seem to be as ceremonious about saying goodbye as in the US. I think that was the same too of the Singaporeans. Kind of interesting because without insight it might feel like someone just kind of ditched you without properly saying goodbye because they didn't like you or something. And of course hugging is not as big as in the Americas 

3) seafood allergy. Met at least 2 VN who are allergic to seafood. Suggests that allergy is likely not a consequence of overcleanliness as in US and EU, but maybe my hypothesis of pollution-induced allergies (since the sea floor is polluted and facilitates bio accumulation of pollutants). Also that's why I think peanut allergies are a thing, because the legumes are buried in the soil and the soil likely had some pollutants. Also because peanuts and nuts are high in lipids so you get bioaccumulation