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A friend of mine was talking about The Iceman, a killer that supposedly used cyanide absorbed through the skin as his murder weapon:

Kuklinski favored the use of cyanide as it was quick kill poison, quicker than either strychnine or arsenic and he would administer it in various ways, he may spray it out of an atomiser type aerosol, or he would accidentally spill it over someone where it would eventually absorb through the skin. Another simple method was just put the cyanide straight onto his victims food, he once took one of his victims out to lunch and put cyanide on his burger.

Is it actually possible to die from absorbing cyanide through the skin?

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  • Also described on his wikipedia page: "He favored the use of cyanide since it killed quickly and was hard to detect in a toxicology test. He would variously administer it by injection, putting it on a person's food, by aerosol spray, or by simply spilling it on the victim's skin." There are no citations and it doesn't state which victims were supposedly killed with cyanide.
    – John Lyon
    Commented Feb 14, 2012 at 6:13
  • I would also think that if it's sufficiently lethal as an aerosol, it would be extremely dangerous to go around repeatedly spraying people. If you get it on yourself you're just as likely to die.
    – John Lyon
    Commented Feb 14, 2012 at 6:20

2 Answers 2

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The World Health Organization report in Concise International Chemical Assessment Document 61: HYDROGEN CYANIDE AND CYANIDES: HUMAN HEALTH ASPECTS

Following application of cyanides in aqueous solution to the intact skin of New Zealand rabbits, the dermal LD50s of hydrogen cyanide, sodium cyanide, and potassium cyanide were 0.260, 0.298, and 0.343 mmol/kg body weight, respectively (corresponding to 6.8, 7.7, and 8.9 mg cyanide/kg body weight) (Ballantyne, 1983a). The dermal toxicity of cyanide, especially of hydrogen cyanide, is markedly greater following application on abraded skin, which enhances the penetration of cyanide (LD50s of 0.087, 0.220, and 0.30 mmol/kg for hydrogen cyanide, sodium cyanide, and potassium cyanide, respectively) (Ballantyne, 1987).5

So, if we assume humans are just like 80kg rabbits, that means that unbroken skin would require 540mg of Hydrogen cyanide or 616 mg of Sodium cyanide.

Hydrogen cyanide is a gas at 26°C, [Wikipedia] so it might be hard to deal with. Let's go with Sodium cyanide, which is a solid that dissolves well into water. At 26°C, Sodium cyanide can be dissolved into water at 52g/100Ml. [Wikipedia], so that corresponds to 1-2 mL of concentrated solution - less than half a teaspoon, for a 50% chance of death.

If you scratch up your victim first, you could reduce it to a 50th of that.

Of course, for governments, Hydrogren Cyanide has plenty of evidence of being a grisly and effective poison: Germany, United States

[Hat-tip to @Fabian who shot down my earlier answer.]

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  • "if we assume humans are just like 80kg rabbits" how useful is that assumption? Is rabbit skin considerably thicker? Was fur a factor? What about internal factors like bloodflow?
    – Sonny Ordell
    Commented Feb 14, 2012 at 7:21
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    (I'm assuming they used a protocol similar to the Draize skin test which involves shaving the skin of the rabbit.) You are asking good questions - animal models aren't perfect, but it clearly isn't ethical to run the experiment on humans, so they are the best we can hope for. Actually, a question about whether animal toxicology testing is meaningful for humans might make a good question, but getting the claims accurate would be tricky.
    – Oddthinking ♦
    Commented Feb 14, 2012 at 7:40
  • That source you quoted says mg, so the amount needed would be 1000 times lower. I'd also think that the numbers for aqeous solutions of cyanide are more relevant, as handling pure HCN at room temperature without killing yourself is not all that easy (boiling point of 26°C).
    – Mad Scientist ♦
    Commented Feb 14, 2012 at 8:01
  • @Fabian, oh the shame! Fixed.
    – Oddthinking ♦
    Commented Feb 14, 2012 at 8:19
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    The thing that will kill you fastest is hydrogen cyanide (HCN): all you have to do is breathe it in. Cyanide salts will convert into HCN in acid environments like the stomach (but there is time to act if you do it accidentally). Apparently, though, they won't kill you if your stomach is alkaline as sometimes happens in alcoholics. It is also easier to detect small quantities of cyanide if you are a smoker. Hence the advice from a chemistry prof I once knew that all cyanide chemists should smoke and drink. He died young of unrelated causes.
    – matt_black
    Commented Feb 14, 2012 at 23:08
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Yes, in chemistry labs Cyanide dissolved in DMSO is referred to as "Liquid Death".

As this in depth explanation states:

The result is obvious: combining DMSO with the wrong compound will rapidly increase the risk of the situation and, if you’re unlucky, the results could be fatal. One such compound DMSO will dissolve is potassium cyanide, making it a liquid that will poison you on contact with the skin or through your gloves. It is not surprising that this mixture of properties has earned it the reputation of ‘Liquid Death’.

This is because DMSO travels straight through your skin, and drags with it dissolved toxins such as cyanide:

Avoid contact with DMSO solutions containing toxic materials or materials with unknown toxicological properties. Dimethyl sulfoxide is readily absorbed through skin and may carry such materials into the body

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    Just as an illustration of DMSO nastiness - if you touch it with a finger then in just a few minutes you start feeling it on your tongue.
    – Cyberax
    Commented Mar 30, 2015 at 6:10
  • I thought liquid death was methylmercury in DMSO.
    – Loren Pechtel
    Commented Mar 14, 2017 at 22:55
  • @LorenPechtel I think that is Liquid Slow Death. ;-)
    – matt_black
    Commented Sep 30, 2017 at 16:43

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