Face Swelling due to an Allergy Underlying Cause
Angioedema occurs when the immune system overreacts to a harmless substance, called an allergen. The immune system is made up of special cells, called white blood cells, which fight infection. When an allergen is present in the body, white blood cells recognize the allergen, and release chemicals into the bloodstream. These chemicals can cause inflammation of the skin, nose, throat, lungs or intestines.
Underlying causes include:
- Baxi S, Dinakar C. Urticaria and angioedema. Immunol Allergy Clin North Am. 2005 May;25(2):353-67, vii. 
- Gompels MM, Lock RJ, Abinun M, Bethune CA, Davies G, Grattan C, Fay AC, Longhurst HJ, Morrison L, Price A, Price M, Watters D. C1 inhibitor deficiency: consensus document. Clin Exp Immunol. 2005 Mar;139(3):379-94. 
- Varadarajulu S. Urticaria and angioedema. Controlling acute episodes, coping with chronic cases. Postgrad Med. 2005 May;117(5):25-31. 
- Zuraw BL. Current and future therapy for hereditary angioedema. Clin Immunol. 2005 Jan;114(1):10-6.