An old-time Finnish bug repellant: pitch oil.
A few weeks ago I heard of a way to keep mosquitoes off: a friend has been ingesting 1 drop of pitch oil a day, in cream or on sugar, for months.
Intrigued, I dug for more data on the oil.
It's "Pyroleum picis", an oil distilled from tar, or an oil distilled from tar and potassium carbonate, K2CO3.
King's only knows Oleum picis, which might fit the bill, but that's distilled out of resinous wood, not from tar proper.
The "oil of tar" which King's mentions is a byproduct of tar production: I've made tar, and you get something called "tar pee" (well, "tervan kusi" in Finnish, which is tar pee), before you get tar proper. That's a thin watery liquid.
Olde folks say not to use pitch oil internally for more than 2-3 days, at a dose of 1-2 drops a day, on sugar or in cream. That's for coughs, not to repel bugs, but the warning stands: I expect the oil is hard on the kidneys (it's distilled from resinous trees), in addition to being a distilled essential oil, which are always difficult, internally.
Olde folks also say to use a drop externally, on the neck, to keep both mosquitoes and horseflies away. And they say that it can be rubbed on horses, but again, not too much of it.
I'll have to get a bottle of the oil and use it as a bug repellant; this year is the year of the horseflies, and it's tedious going out to pick herbs on dry meadows with 3 or 4 different kinds of horsefly trying to get a bite in.
And while this year's mozzie season is almost over, there'll be more of those next year.