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Risks associated with Aspirin Mask?

Having read some threads praising aspirin masks, I'm beginning to ponder on some potential hazards related to it.

The basic principle behind aspirin mask is to hydrolyse Aspirin (acetylsalicylic acid) into Salicylic acid and Acetic acid (found in vinegar).

Salicylic acid is indicated as a treatment for many skin related problems, with concentrations ranging from 0.5% to 27%. It's not as widely used as other chemical peels for improving skin condition, mainly because high concentration can result in Salicylism, which is of course a health risk.

Now if you go on sites recommending aspirin mask, the typical recipe is to crush 4-5 uncoated aspirin tablets and dissolve in 1 tea spoon (5ml) of water.

Doing some rough (might be wrong) calculations (Good way to revise for my pharmaceutical calculations :rolleyes: ), assuming that 5x 500mg aspirins are to be dissolved in in 5ml water.

2500mg = 2.5g. Molecular weight of Aspirin is 180.16. Moles = Mass/MR, Moles = 0.01388

Since it's a 1 to 1 reaction. You will also get 0.01388 moles of salicylic acid and 0.01388 moles of water will be used.

Mass of salicylic acid formed = 0.01388 x 138.12 = 1.917g.

For water, 1ml = 1g. Mass of water used = 0.01388 x 18.02 = 0.250g = 0.250ml.

So it's 1.917g of Salicylic acid in 4.750ml of water. Pharmaceutical % concentration are usually calculated in %m/v. So:

1.917g/4.750ml, to get it to %m/v, x 21.0526 = 40.36g/100ml.

That's 40.36% concentration

It's a conservative calculation as the other constituents in the tablet may react with water and thus further increase the concentration.

so 5 x 500mg in 1 teaspoon = 40% salicylic acid. Very high and certainly won't do you much good. There are also a lot of people crushing MORE tablets and dissolve it in LESS water, whilst doing it religiously.

Disclaimer: I might screw up the calculation, if I do, please do point it out to me.

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Glad to see that there is a fellow supergeek out there.......

You calculations are fine actually, assuming that the acetylsalicylic acid is completly hydrolysed by the water.....and since acetylsalicylic acid isn't very water soluble the hydolysis is most likely not complete. Which means that one mole of acetylsalicylic acid dosent equal 1 mole of salicylic acid and one mole of acetic acid. This depends on the kenetics of solution and hydrolysis. Also the hydrolysis is way more efficient at a higher pH. The solubility of asprin in water is 1g/300g, which is pretty low........this would have to factor into the caculation......also it depends on if you are dissolving buffered asprin in the water or not.........The hydroysis of acetylsalicylic acid into salicylic acid and acetic acid is gradual and rather slow.....and if the mixture is applied to the skin there is most likely more acetylsalicylic acid then salycilic acid or acetic acid.........

And in order for it to actually cause salicylism a signifigant quantity of salicylate must be absorbed through the skin......

What you have shown is a worst case scnerio.......

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