Topical castor oil appl'd to hands - dev'd painful welts a few days later & immed'y discon'd use. still have the welts wonder if it's an allergic reac?

Likely: Try some Benadryl (diphenhydramine) spray in that area and topical cortisone like Hydrocortisone 1 % over the counter. You may also take antihistamines by mouth (like Loratadine 10 mg qd or Allegra or zyrtec during day time) or Benadryl (diphenhydramine) or chlortrimeton at night. If significant swelling of lips or wheezing or shortness of breath go to dr or emergency room asap.