Why is your earlobe swollen red and hot if you have an outer ear infection?

Edema: The outer infection causes two things... Edema (congestion of the lymphatics) and drainage, bot of which cause the swelling. If it is to that point, you need antibiotics.

Otitis externa: An outer ear infection (or swimmers ear) can be quite painful and causes swelling of the ear canal and outer ear and lobe (in some cases). These infections require drops at a minimum and may require oral antibiotics.