This definitely sounds like an allergic response. You could try anti-histamine tablets fro the pharmacist. Get either Benadryl allergy relief, Clarytin or Piriton tablets and give 1/2 tablet 3 to 4 times daily. This should relieve some of the allergy symptoms. In severe cases of allergies, if she is breaking the skin scratching, short courses of steroids are needed from your vet.
Hope this helps