These questions are ones I could probably answer but with a bit of help - they're a bit outside my domains of knowledge, but not so far that I can't have a stab at them.
Do some ingredients in deoderants introduce harmful toxins into our body via absorption?
I assume this question has been asked by someone who might have genuine concerns about 'toxins' and ingredients in deodorants - this sort of thing comes up every now and again I suppose. Seems like a good opportunity to reassure...
What factors determine whether something can be absorbed across the skin? I'm assuming 'size' (molecular mass) plays some role? Gosh I used to know this! and lipophilicity. Anything else? Does the pH make much of a difference (beyond the seriously high molarity acids that would just be wrecking the skin to the point that all sorts of things could suddenly get across).
Nicotine (C10H14N2) gets across the skin with ease, or at least that's what I'm led to believe (does it have to be specially formulated in those patches?) but glucose (C6H12O6) which is of a similarish magnitude doesn't, I have always assumed because it's water soluble but not fat-soluble whereas nicotine's a bit amphiphilic (soluble in polar and non-polar solvents).
What's the maximum size of something that can be absorbed get across the skin? You can bully larger or more polar molecules across the skin with electroporation but that's not really relevant to deodorant use!
Does drinking acid (e.g. lemon juice) with alcohol prevent from being drunk by transforming alcohol in ester? Alcohol + Acid = Ester + Water.
Someone's already provided a sensible answer ('no', with a bit more detail) so there's less urgency on this one. But I think what's missing is that 'alcohol' when drunk in a beverage is about 95 per cent water whereas this equation doesn't seem to take account of that. The first answer references stomach acid anyway which I think is probably a rather good point.
The only way I can see how this would work would be to combine pure alcohol and an acid together beforehand so that you were actually drinking an ester - this would guarantee not getting drunk, and feeling a bit queasy in the process no doubt.