The most common side effects from collagen stimulating injections are minor but can include tenderness or pain, redness, bruising or swelling. These side effects generally last between two to six days. It is not uncommon to bruise with collagen stimulating injections treatments with up to 20% of patients experiencing some bruising. However, this can be concealed with makeup. Small early nodules may sometimes occur but often resolve spontaneously within three to four weeks. The development of late nodules is uncommon.