[Tilted Irish Kilt]

Fai Mao :" I saw a health worker once tell children to sing “Happy Birthday”
while they wash their hands because it takes that long to thoroughly wash the hands."

I heard that too !
My understanding is that it should take about 20 seconds to raise a good soap lather
in order to flush away any surface contaminants and bacteria.
You were wise to listen .. and follow that advice !

[Vermont Lt]

We had a saying in the hospital, wash in, wash out. Damn your hands got leathery.