The other name for Angioedema is Skin Hives. There can be many reasons for the the spots that have grown on your left arm; like allergy from any food substance or from any particular drug.
Hives is a very serious skin disease that should not be taken lightly. To cure you of the skin hives on the left arm, take 6 table spoon of oatmeal and 3 table spoon of starch grain and mix them well in a bucket full of water. Bathe in that water and continue the procedure for 2 weeks. At the end of 2 weeks, the spots from your arm will be gone.
If the hives are not gone, then I would suggest you to use Oxy-Hives.
It is a homeopathic treatment that is available in spray form. A friend of mine had developed serious skin hives on his body. He used this ointment for 2 months regularly and was then cured of this disease.
For more information about Oxy Hives, visit:
http://www.hives-treatment.net