or is that just an urban legend claim?
Sauna that was built then wasn't just one hot room, but it also had at minimum small changing room dressing/undressing, relaxing between turns in steam room. Also if it was first building made then adding also lounge which served as living space with beds and cooking stove while building house was common. With sauna you had place to stay warm first winter, able to get warm water, wash clothes, yourselves and even a give birth old times. Building sauna first made lot of sense.
These days sauna for home builders is more about getting sauna somewhere in that floorplan where works well for the intended users of that house.
wouldn't a kitchen accomplish that goal better?
I personally dont know how tar was used for health, but it was big export item of Finland during medieval times.
[1]https://www.helsinkitimes.fi/themes/themes/health-a-wellbein...
Now, there are things like Fucidin, Polysporin and silver ointment for infected wounds and burns, respectively, that are safer and more effective.
Some people still swear by it, because “tradition” and probably some element of malignant patriotism too.
Another weird/fun one is using bleach as an anti-inflammatory (topical only, of course...), although these days you can find derivative products that offer the same benefits but are much less harsh.
Not to be done too often but every once in a while I find it helpful. Not all that different from a strongly chlorinated pool.
Another cool one, especially if you don’t have a sauna, is doing a mustard bath. You will sweat like a stuck pig
It's used small amounts in additive in soap or shampoo mostly as a scent, mouth pastille and lozenge a for taste, animal health care kind antibacterial and bug resistant etc. long time ago.
Quite lot of applications especially old times long time ago before more scientifically developed medicines were commonly available. These days less there but it's used as a scent or for flavour.
Smells good, for sure. But I don't know if it promotes good health.