Some lesions, such as whiteheads, heal quickly and without scarring. Other lesions, such as inflammatory nodules and cysts, can take longer to heal and may leave severe scars.
Regardless of the type of lesion, however, the fundamental process of healing is the same, involving these three phases:
- Inflammatory phase: The body reacts by sending in inflammatory molecules to start the process of healing, and blood vessels dilate.
- Healing phase: Skin proteins join in and start rebuilding the skin.
- Remodeling phase: This is a "clean up" phase that tidies up the extra skin proteins from the healing phase and returns the skin to normal.
Acne is primarily an inflammatory disease. In fact, inflammation is present throughout the entire cycle of an acne lesion, from before a recognizable lesion even forms all the way until the lesion is healed.
Inflammation is present in all types of acne lesions, including:
- Microcomedones (microscopically tiny clogged pores).
- Whiteheads and blackheads, which scientists call “non-inflammatory lesions” because they are not red and sore. Regardless of the name “non-inflammatory lesions” there is still some inflammation present.
- Papules, pustules, nodules, and cysts, all of which scientists call “inflammatory lesions” because they are red and sore.1
According to a 2014 article in the Journal of Drugs in Dermatology, “Recent research has confirmed that inflammation is the hallmark of all acne lesions.”1
While inflammation occurs in all acne lesions, different types of lesions have different amounts of inflammation associated with them. The amount of inflammation determines how quickly an acne lesion heals and affects whether the lesion leaves a scar when it heals. For example, whiteheads and blackheads typically have minimal inflammation and heal within 7-10 days without scarring, while inflammatory nodules and cysts have extensive inflammation and take longer to heal and can leave severe scars.1-2
The Process of Healing Acne Lesions
Regardless of the type of lesion or amount of inflammation present, the fundamental process of healing acne lesions is the same for all lesions and looks like this:
- Step 1: The first step in healing acne lesions is an inflammatory phase, in which immune cells surround the skin pore and produce inflammatory proteins. These inflammatory proteins cause the surrounding blood vessels to dilate (expand), resulting in the redness that is characteristic of inflammation.
- Step 2: The second step is a healing phase, in which a variety of cells become active that help build the skin’s structure. These cells produce structural proteins such as collagen and keratin that help restore the skin’s normal structure. This phase ultimately results in an excess of these proteins surrounding the lesion.
- Step 3: The final step is a remodeling phase, in which proteins called metalloproteinases break down the extra proteins from the healing phase, so that the lesions heal without any extra skin tissue. We can think of this final step as a “clean-up” phase, in which the metalloproteinases tidy up the mess that was left behind during the healing phase. Depending on the severity of the original lesion, the remodeling phase can last up to several months. The degree of inflammation present in the acne lesion affects what happens during the remodeling phase, and that affects whether or not a scar forms when the lesion heals. Acne lesions with more extensive inflammation leave scars when they heal, while those with less inflammation often heal without scarring.3-4
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- Kircik, L. H. Re-evaluating treatment targets in acne vulgaris: adapting to a new understanding of pathophysiology. J. Drugs Dermatol. 13, s57–60 (2014).
- Goodman, G. J. Post-acne scarring: A short review of its pathophysiology. Australas. J. Dermatol. 42, 84–90 (2001).
- Saint-Jean, M., Khammari, A., Jasson, F., Nguyen, J.-M. & Dréno, B. Different cutaneous innate immunity profiles in acne patients with and without atrophic scars. Eur. J. Dermatol. 26, 68–74 (2016).
- Shih, B., Garside, E., McGrouther, D. A. & Bayat, A. Molecular dissection of abnormal wound healing processes resulting in keloid disease. Wound Repair Regen. 18, 139–153 (2010).