My Father Is Having An Allergic Reaction To Ammonium Lactate.

My father is having an allergic reaction to ammonium lactate. Both arms are deep red itchy swelling. His Dr said stop using which he did but after a week no improvement, no advice from dr to clear up side effects. My dad is 90 and very uncomfortable. Would alleges or Claritin help. He finished 6 weeks radiation on his face in april. Problem more under the skin like bruising and purplish more than surface rash.