As I understand it, acids are substances which have a high concentration of H+ ion which makes acid an acid. When interacting with our skin, acid can damage it. How does this concentration of protons cause damage to skin?

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    $\begingroup$ Those protons don't simply sit around doing nothing. They tend to bind to/attack the polymers (keratin and such) that make up your skin and form newer, smaller molecules; i.e- it breaks down the polymers that constitute your skin. The stronger the acid is, the higher the concentration of protons in it, and hence, greater the tendency/chances of them binding to your skin. $\endgroup$ Jul 20 '17 at 5:08
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    $\begingroup$ Also there is a relay proton distribution mechanism which accelerates the impact pointed out by @paracetamol. $\endgroup$
    – andselisk
    Jul 20 '17 at 6:20
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    $\begingroup$ Not only high pH but also concentration of anions is dangerous. $\endgroup$
    – Mithoron
    Jul 20 '17 at 13:31
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    $\begingroup$ @Mithoron High pH is indeed dangerous (dissolves the skin tissue), but acids have low pH. And skin is fairly resistant even to strong acids. The problem are indeed the anions (e.g. the notorious fluoride) and undissociated acids that diffuse through the skin. $\endgroup$
    – Karl
    Jul 20 '17 at 16:38
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    $\begingroup$ In addition, the corrosive (to be taken in a broad sense, here) property of many acid does not result from - or not only from - their ability to donate protons but from their chemistry as a whole . They can dehydrate and oxidize almost everything in the tissues, (eg H2SO4), undergo specific reaction (eg HNO3 reacts with proteins to give yellow xanthoproteins), etc. $\endgroup$
    – Alchimista
    Jul 20 '17 at 20:52

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