By Kylie Nicholson

FEB 16, 2023

Our skin doesn’t just serve as a key part of our outward appearance. It is a functional organ tasked with protecting our bodies from external aggressors and armed with the amazing ability to regenerate itself when damaged.

The body’s mechanism for repairing damaged tissue is an organized and dynamic process achieved through four main steps that are initiated by our largest organ - skin. This blog will discuss the four main stages of wound healing, along with signs of proper wound healing.¹ The body’s wound healing process starts as soon as an injury occurs. Blood cells called platelets are the first responders at the wound site. These platelets release chemicals into the bloodstream called cytokines to alert the body’s wound healing stages to start. White blood cells called neutrophils are also present immediately at the wound site to prevent infection from foreign bodies that can enter the body through the wound bed.² The first stage of wound healing, hemostasis, begins immediately at the onset of an injury.¹

• Hemostasis: The goal of hemostasis is to occlude the wound to prevent infection and further damage happening to the body. This is where the emergency repair system, blood clotting, takes place. Blood clotting creates a temporary barrier to stop bleeding and protect the body from foreign particles entering at the site of injury.³
• Inflammation: The goal of this phase is to clear foreign bodies and bacteria from the wound in order for the body to be able to start the regrowth of tissue.³ The inflammatory phase is commonly exhibited by swelling, pain, heat, and redness.¹
• Proliferation: During proliferation, the wound is filled in with new tissue. The edges of the wound shrink during this stage as the new tissue closes across the wound bed. The new tissue, called granulation tissue, is light pink or red in color, uneven in texture, and does not bleed easily.³
• Maturation: In the last phase of wound repair, the collagen fibers from earlier stages are restructured to have a more smooth texture, greater tensile strength, and flexibility. Maturation can last anywhere from 21 days to 2 years, depending on the placement and severity of a wound.³

• Hemostasis: Blood clotting occurs when platelets come into contact with collagen to form clots. These clots are attached together with the help of the enzyme thrombin to create a mesh that covers the wound and secures the clot in place.³
• Inflammation: Inflammation allows repair cells to move freely across the wounds to heal the skin. Inflammation is caused by the white blood cells, growth factors, and enzymes that are brought to the wound during this stage to remove any debris and germs in order for the body to progress to the next stage of wound repair.¹
• Proliferation: The new tissue that grows in the wound during proliferation is composed of collagen and extracellular matrix. New blood vessels are created in the forming tissue to allow for oxygen supply to return to the area.¹ At the end of proliferation, epithelial cells resurface the wound. ³
• Maturation: During maturation, the reparative cells from earlier wound healing stages are removed by apoptosis, or programmed cell death. Water is reabsorbed allowing for collagen fibers to cross-link together. Even with the stronger cross-linked fibers, the tensile strength of the connective tissue during maturation is only about 80% of what it was before the area incurred an injury.¹

Wounds typically take between 4-6 weeks to fully heal.⁴

• Hemostasis begins immediately and finishes when the bleeding has stopped.⁵
• Inflammation lasts between 4-6 days and begins when hemostasis has finished.³
• Proliferation lasts from between 4 and 24 days. There is no set beginning and ending times to proliferation as it occurs simultaneously with the other phases.³
• Maturation occurs around 3 weeks into the healing process and can last as long as 12 months.⁴

What color should a healing wound be?

Inflammation is often paired with a red color and swelling in the area. ¹ The new tissue created during the proliferation phase is first a deep red color as new blood vessels are created. Later in proliferation, the tissue often appears light pink or red in color.³Therefore, it is perfectly normal to have a healing wound appear red and pink, especially in the beginning stages of the healing process.

How do you know if a skin wound is healing well?

If the newly forming tissue that appears during the proliferation phase of healing appears pink or light red, the wound is likely healing well and free from infection. However, if this new tissue is coming in dark, it could be a sign of infection or a lack of blood supply to the area, which will likely cause slow wound healing. Also, wounds that progress quickly through the stages of healing are likely healing well.¹

Signs of infection in a wound include pus, fever, increased redness and swelling, and warmth radiating from the wound. This can occur if bacteria managed to enter the wound and the white blood cells introduced during inflammation weren’t able to remove the infection. This can be avoided by cleaning the wound site soon after it appears, keeping the wound dressed with clean gauze, and changing the dressing regularly.⁶

Tips for Helping a Wound Heal

In order to allow a fresh wound to heal correctly, it is important that the wound stays clean and undisturbed during the healing process.⁶ If you suffer a superficial wound that is small enough to treat at home, follow these steps to allow for a quick recovery, and always consult a physician if you’re in doubt of what to do:

1. Start with clean, dry hands before touching the wound. If there is bleeding, apply pressure to the wound with a clean bandage or gauze, and elevate the wounded area.⁷
2. Wash the wound immediately with clean water to remove any debris from the area. Clean around the area with warm soapy water to disinfect.
   Hydrogen peroxide is not recommended for use on open wounds because it can irritate the skin and may contribute to delayed wound healing.⁶
3. Cover the wound bed with a clean gauze or bandage to prevent the wound site from coming into contact with dirt and bacteria. Change the dressing daily, when it becomes wet or dirty.⁷
4. Consistently apply topical skin care products that will help support the wound healing process while combating scar formation.
5. Take note of which foods to avoid during wound healing as diet plays a significant role in healing skin from the inside out.

Key Takeaways

• The four stages that wounds progress through while healing are hemostasis, inflammation, proliferation, and maturation
• Wounds typically take between 4 and 6 weeks to heal, but can take longer if the wound becomes infected or is disturbed
• It is normal for wounds to have a pink or reddish appearance during the healing process
• Keep wounds clean and dry to allow for quick healing of damaged tissue and to prevent infection

By Kylie Nicholson:
Kylie is studying Biosystems engineering at the University of California, San Diego. She is passionate about scientific writing and women's health research.

Sources:

1. https://www.woundsource.com/blog/four-stages-wound-healing
2. https://askabiologist.asu.edu/explore/when-body-attacked
3. http://www.shieldhealthcare.com/community/popular/2015/12/18/how-wounds-heal-the-4-main-phases-of-wound-healing/
4. https://www.ncbi.nlm.nih.gov/books/NBK470443/
5. https://www.healthline.com/health/skin/stages-of-wound-healing#stages-of-wound-healing
6. https://www.medicalnewstoday.com/articles/325040#prevention-and-treatment https://www.mayoclinic.org/first-aid/first-aid-cuts/basics/art-20056711