The thing is people buy them. I have been asked for things like this before ....
There is nowt stranger than folk
I can see the attraction for worn underwear to be honest. Maybe I am admitting I am strange for that though.
But a bottle of saliva or pee is just gross, and would also get her in big trouble if the post man opened it for inspection as its illegal to post bodily fluids in the post unless you adhere to strict safety/packaging policies. Which I doubt the girls that do it will (sorry for being a downer to the girls, but just remembered it)
The packaging must consist of three components:
(a) a primary receptacle(s);
(b) a secondary packaging; and
(c) a rigid outer packaging.
Primary receptacles must be packed in secondary packagings in such a way that, under normal conditions of transport,
they cannot break, be punctured or leak their contents into the secondary packaging. Secondary packagings must be
secured in outer packagings with suitable cushioning material. Any leakage of the contents must not compromise the
integrity of the cushioning material or of the outer packaging.
They will likely chuck the bottle in a padded envelope.