The Collaborative International Dictionary of English v.0.48:

Wheal \Wheal\, n. [OE. whele, AS. hwele putrefaction, hwelian to
   putrefy.]
   A pustule; a whelk. --Wiseman.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Wheal \Wheal\, n. [Cf. Wale.]
   [1913 Webster]
   1. A more or less elongated mark raised by a stroke; also, a
      similar mark made by any cause; a weal; a wale.
      [1913 Webster]

   2. Specifically (Med.), a flat, burning or itching eminence
      on the skin, such as is produced by a mosquito bite, or in
      urticaria.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Wheal \Wheal\, n. [Cornish hwel.] (Mining)
   A mine.
   [1913 Webster]

WordNet (r) 3.0 (2006):

wheal
    n 1: a raised mark on the skin (as produced by the blow of a
         whip); characteristic of many allergic reactions [syn:
         wale, welt, weal, wheal]