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]

Moby Thesaurus II by Grady Ward, 1.0:

61 Moby Thesaurus words for "wheal":
   abscess, aposteme, bed sore, blain, bleb, blister, boil, bubo,
   bulla, bunion, canker, canker sore, carbuncle, chancre, chancroid,
   chilblain, cold sore, eschar, felon, fester, festering,
   fever blister, fistula, furuncle, furunculus, gathering, gumboil,
   hemorrhoids, kibe, lesion, papula, papule, paronychia, parulis,
   petechia, piles, pimple, pock, polyp, pustule, rising, scab,
   soft chancre, sore, stigma, strake, streak, stripe, sty,
   suppuration, swelling, tubercle, ulcer, ulceration, wale, weal,
   welt, whelk, whelp, whitlow, wound