What is the reason for redness and swelling 3 days after circumcision surgery?

Patient's question:

It has been three days since the surgery today. I have received anti-inflammatory injections for three days, undergone two days of infrared light treatment, changed the gauze twice, and received another anti-inflammatory injection today. The attending doctor also asked me to do infrared light treatment again, but I didn't do it. I would like to ask, what is the reason for the redness and swelling three days after a circumcision?

Doctor's answer:

Postoperative Precautions
1. The surgical procedure takes approximately 15–25 minutes and does not require hospitalization.
2. Mild pain and bruising may occur at the wound site after surgery. Pain relievers should be taken regularly, and the wound should heal within 7–10 days.
3. Before the wound fully heals, follow-up check-ups should be scheduled periodically.
4. Keep the wound clean and dry after surgery. Be cautious not to wet the gauze when urinating.
5. The wound is sutured with absorbable stitches, so there is no need for suture removal.
6. If an erection occurs, use one hand to protect the wound and firmly press the glans with the other hand to allow the penis to naturally subside, preventing the wound from tearing open.
7. If the wound swells, aches, or develops an open sore, apply local cold compresses and ointment for relief. In cases of severe sores, seek immediate medical attention.