What Causes Acne Marks to Darken Over Time
Acne marks, often called post-inflammatory hyperpigmentation or PIH, start as flat brown or dark spots left behind after pimples heal. These spots form when inflammation from acne triggers skin cells called melanocytes to produce extra melanin, the pigment that gives skin its color.[1][2] Over time, certain habits and exposures can make these marks darker and harder to fade.
Sun exposure tops the list of culprits. Ultraviolet rays from the sun stimulate melanocytes to crank out even more melanin, turning light marks into deeper brown or black ones.[1][2][4][5][7] This happens because UV light breaks down skin proteins like collagen and elastin while boosting pigment production, especially in people with medium to darker skin tones that tan easily and hold color longer.[2][5] Even short time outdoors without protection can darken spots and delay healing by months.[1]
Picking or squeezing pimples adds extra damage. When you touch or pop acne, it causes more inflammation and trauma to the skin, signaling melanocytes to overproduce melanin and create worse discoloration.[1][2] What might have been a small mark turns into a stubborn dark patch because of this added injury.
The original acne type matters too. Deeper, inflamed breakouts like cysts or nodules stir up stronger inflammation, leading to more melanin and darker marks from the start.[1][2] These spots then darken further with sun or picking.
Skin tone plays a role in how much marks darken. Folks with Fitzpatrick skin types III to VI, often medium to darker tones, have more active melanocytes, so their PIH builds up faster and lasts longer under the same triggers.[2]
Other factors like hormones or certain medications can indirectly worsen things by ramping up melanin, but sun and picking stand out as the main everyday causes.[3]
Sources
https://worldofasaya.com/blogs/acne/post-acne-hyperpigmentation-your-complete-guide
https://www.kins-clinic.com/blogs/acne-marks-or-acne-scars-understanding-the-difference-and-management-options
https://www.youtube.com/watch?v=Ro1j61PZYKQ
https://www.aesthetispa.com/blog/3-things-making-your-acne-scars-worse-and-what-you-can-do-about-it/
https://www.cvs.com/learn/beauty/skin-care/acne-scars
https://slmdskincare.com/blogs/learn/the-5-kinds-of-acne-scars-how-to-treat-each-type
https://amvital.com/blogs/blog/teen-acne-marks-fade-dark-spots
https://consciouschemist.com/blogs/good-skin-blog/how-to-treat-acne-without-dark-marks-or-scars
