Are burns from Lye or Potash that bad?
As noted in the comments, lye burns are very damaging to skin and especially mucous membranes. This damage can be drastically reduced if the lye is washed off as quickly as possible.
One reason that these solutions are considered particularly dangerous is that there is no discomfort immediately upon contact (in contrast to acids, which tend to produce burning sensations immediately). Instead, the affected surface simply feels a bit soapy.  As a result, the presence of lye on skin may not be noticed until it is too late to prevent damage by washing.
On a side note, the &quot;it's sold in hardware stores&quot; argument is not a good test for chemical toxicity. There are numerous highly toxic chemicals that can be purchased readily.