If you have allergies, you may notice that your eyes or lips may become puffy or swollen. This is a condition called angioedema. Angioedema is swelling in the deep layers of your skin and mucous membranes. It's like hives, which it often occurs with. But angioedema doesn't cause your skin to itch. Hives cause itching. The swelling you have with angioedema is caused by leaky blood vessels. Part of your blood, called plasma, leaks into the tissue under your skin and mucus membranes. This causes these tissues to swell.