[ROCKLOBSTER]

as a child during the late '60's through the '70's is that there were very few kids with asthma and allergies in general, despite cigarette smoking being quite common.

Didn't the "WHO" (World Health Organization-UN) sometime back, declare second hand smoke to have a health benefit, for the reasons you just mentioned. (builds up their immunity)

[RegulatorCountry]

I don’t know, but I do distinctly recall blowing cigarette smoke into your ear as being regarded as helpful for an earache, I recall it helping me at least, whether it was psychological or what I couldn’t say being a child at the time. Sounds weird now, I know.