Ok so usually when I get a pimple, it will be red and swollen for maybe 2 days and on the third day, it will have pus and I can pop it. Then it can start to heal and form a dark spot etc. (which can be more annoying than the pimple sometimes). Anyway so when I was taking oral antibiotic (erythromycin 250 mg every night), I noticed that if I got a pimple, it would stay red and swollen for maybe 5-6 days and then form pus instead of the usual 2-3 days. Now when I have stopped the oral erythromycin and started topical again (benzamycin) I have noticed that if I do get a pimple, it will heal within 2-3 days like before. So I am glad I stopped the oral antibiotic.