Purple Bruise-like spot on my lower and upper lip

For the past year I've experienced random swelling on the upper right and the lower bottom part of my lips about 6 times. The only thing I've linked to the swelling is when I feel my blood temperature rise. My lips stay swollen for about a day then they gradually go back to normal and a purple bruise-like spot stays for a couple more days. In the beginning, the purple spot faded after about a week from the swelling, but with the last swelling incident the purple color has not gone away. Do you know what is causing the swelling? Is the purple spot now permanent or is there something I can take or do to get rid of the discoloration?