What could be the reason for having swelling in random places on the body?

Angioedema. This condition can be acquired or hereditary and is worth consulting a physician for work up and management.
Need more info. More information is needed. More questions: where is the swelling and how long have you had it? Does it seem to come and go in different locations or in the same location? Any rash? Any other infection or fever? Any redness? Is it both sides of the body, ex both hands, or different sides of the body?