Why do spots appear? The three stages of acne and where LED light works
by LauraShare
A spot doesn't appear overnight. By the time you see it in the mirror, the process that formed it has been under way for days or weeks inside a duct less than a millimetre wide.
A spot forms in three stages: the pore stops emptying, sebum gets trapped and inflammation is triggered. Understanding this chain explains why treating only the visible spot isn't enough, and where LED light fits in.
How does a spot form?
A spot is the end result of a chain that begins inside the follicle, long before there's any bump or redness on the surface. It all starts with the microcomedone, a microscopic plug of cells and sebum that can't yet be seen from the outside, but that can develop into any of the visible forms of acne (Vasam et al., 2023).
| Stage | What happens inside the pore | Can you see it? |
|---|---|---|
| 1. Blocked pore | Dead cells build up in the duct instead of coming out | No |
| 2. Trapped sebum | The gland keeps producing sebum, but it no longer has a way out | Not yet |
| 3. Inflammation | The environment changes, C. acnes becomes active and the immune system responds | Yes, the spot appears |
Stage 1: the pore stops emptying properly
What we call a pore is the opening of a duct. Its wall is lined with cells that renew constantly and that, in skin without acne, come away one by one and are carried out by sebum.
In an acne-prone follicle this turnover becomes disordered: the cells divide faster and come away stuck to one another, instead of one by one. They stay inside and start to form a plug in the last section of the duct, the infundibulum (Vasam et al., 2023).
At this point there's nothing red on the surface. And yet, this is the stage that decides the next breakout.
Stage 2: sebum gets trapped
The sebaceous gland keeps producing, but the exit has narrowed. Sebum is held between those cells and helps compact the plug.
Sebum isn't just oil. Its composition matters more than its quantity: when it stays trapped, some of its lipids are transformed. One of them, oxidised squalene, encourages the cells in the duct to build up even more and activates inflammatory signals (Ottaviani et al., 2010). In other words, trapped sebum doesn't just take up space, it also keeps the blockage going.
That's why cleansing harder doesn't fix the problem. Oil is made by the gland; water is held by the outermost layer of the skin. A harsh cleanser leaves the skin tight while the gland keeps producing just the same (Jordan and Baldwin, 2016).
Stage 3: inflammation is triggered
The blocked pore creates a different environment: less oxygen gets in and more sebum is available. That's where the activity of Cutibacterium acnes (C. acnes) changes, a bacterium that's part of the skin's normal microbiota and is present in skin with and without acne (Dessinioti and Katsambas, 2024).
In that environment, the bacterium transforms the lipids in sebum and releases molecules that the skin recognises as an alarm signal. The cells of the follicle respond with inflammatory mediators such as IL-1β and IL-8, the follicle wall weakens and, when it gives way, the visible spot appears (Dreno et al., 2015).
Bacteria don't start the process, they amplify it. Inflammation had already begun while the microcomedone was forming, before there was anything red on the surface (Dreno et al., 2015).
Don't treat the spot, break the chain
When a spot disappears, there may be other follicles in the same area at stage 1 or 2 that can't be seen yet. That's why acne is controlled by acting on the whole chain, consistently, rather than chasing each spot one at a time.
No single treatment acts on all three stages at once:
| Stage | What can help |
|---|---|
| 1. Blocked pore | Topical retinoids act on the formation of new microcomedones, with an effect that builds over several weeks (Reynolds et al., 2024) |
| 2. Trapped sebum | A routine that respects the skin barrier, so treatment can be kept up without irritation (Jordan and Baldwin, 2016) |
| 3. Inflammation and bacteria | Blue light acts on the bacterial component; red and infrared light act on inflammation and tissue recovery (Diogo et al., 2021; Hernández-Bule et al., 2024) |
How does an LED mask work on acne?
LED light acts on stage 3 of the chain, and it does so in two complementary ways.
Blue light acts on the bacterium; it doesn't attack the skin. During its metabolism, C. acnes produces porphyrins, molecules that absorb light in the blue region of the spectrum. When they receive that energy, they generate reactive species capable of altering the bacterium (Diogo et al., 2021).
Red and infrared light work on inflammation. They penetrate further than blue light and act on the mitochondrial metabolism of cells, modulating the inflammatory response around the follicle and tissue recovery (Hernández-Bule et al., 2024).
| Light | What it brings to acne |
|---|---|
| Blue (465 to 470 nm) | It acts on the bacterial component of active breakouts |
| Red (630 to 635 nm) | It modulates inflammation and the tissue response around the follicle |
| Near infrared (830 to 835 nm and 930 to 935 nm) | It supports inflammatory modulation and tissue recovery |
| Deep infrared (1072 nm) | It reaches deeper layers and focuses on cellular modulation and tissue recovery |
Unlike some lasers, LED doesn't cause thermal injury, so it can be repeated regularly. And that's exactly what a chain that reactivates in different follicles every week needs.
Silicone LED Mask: blue, red and infrared light in a single routine
The Silicone LED Mask combines the four bands in the table above, with more than 200 diodes across the face module and the neck and décolletage piece, five power levels, sessions of 10 to 30 minutes and an irradiance of 30 mW/cm².
- It acts on active breakouts with a bacterial component, thanks to blue light.
- It helps modulate inflammation with red light and the infrared bands.
- It supports tissue recovery around the follicle.
- It reaches the back too: the neck and décolletage piece can be placed on the back, an area that's hard to reach and where lesions also form.
Results start to show from day 28, always within the recommended protocol. The Silicone LED Mask complements your usual skincare routine and cosmetic and medical aesthetic treatments.
Explore the Silicone LED Mask →
Why consistency matters more than intensity
Photobiomodulation follows a biphasic response: too low a dose doesn't generate the stimulus, but going beyond the right range doesn't increase the benefit either (Huang et al., 2011). Making a session longer is no substitute for regularity.
Since follicles in the same area are at different points in the chain, repetition makes it possible to reach them at different stages. An inflamed spot may improve before new breakouts become less frequent, because microcomedones need time to develop. Improvement is assessed over weeks, not by what happens with a single spot.
When to see your dermatologist
- Nodular lesions that are deep or painful.
- Breakouts that leave scars.
- Acne that doesn't respond to treatment after several weeks.
- Very irregular cycles, increased hair growth, androgenic pattern hair loss or a sudden onset of acne.
The window to prevent a scar lies in the active phase, so the sooner, the better.
This content is for informational purposes only and doesn't replace a medical assessment.
Frequently asked questions
How long does a spot take to form? By the time a spot becomes visible, the process has been under way for days or weeks. It begins with the microcomedone, a microscopic plug that can't be seen from the outside.
Is acne caused by bacteria? Not exactly. C. acnes lives on the skin naturally, with and without acne. What changes is its activity inside a blocked pore: it doesn't start the process, it amplifies it.
Does blue light get rid of spots? Blue light acts on the bacterial component of active breakouts through the porphyrins produced by C. acnes. It doesn't act on the blockage of the pore, which is why it's combined with red and infrared light and a consistent routine.
Why does another spot appear as the last one disappears? Because follicles in the same area aren't at the same stage. While one resolves, others contain microcomedones that can't be seen yet.
Can I use the LED mask for longer to see results sooner? No. Photobiomodulation follows a biphasic response: going beyond the right range doesn't increase the benefit. Frequency and duration should stay within the device's protocol.
In summary
A spot forms in three stages: the pore stops emptying, sebum gets trapped and inflammation is triggered when C. acnes becomes active in that environment. What you see in the mirror is only the last link. LED light acts on that final link, blue on the bacterium and red and infrared on inflammation, and it works better with consistency than with intensity. Don't treat the spot: break the chain.
If you'd like to go deeper into hormones, stress, marks and scars, read our article Adult acne: why a spot starts weeks before you can see it or download SKINVITY's Adult Acne Guide →
The SKINVITY Team
Scientific references
The following references correspond to the general scientific evidence on acne and photobiomodulation cited in this article, not to an efficacy test specific to a SKINVITY device.
- Vasam M, Korutla S, Bohara RA. Acne vulgaris: a review of the pathophysiology, treatment, and recent nanotechnology based advances. Biochem Biophys Rep. 2023;36:101578.
- Ottaviani M, Camera E, Picardo M. Lipid mediators in acne. Mediators Inflamm. 2010;2010:858176.
- Jordan L, Baldwin HE. Stratum corneum abnormalities and disease-affected skin: strategies for successful outcomes in inflammatory acne. J Drugs Dermatol. 2016;15(10):1170-1173.
- Dessinioti C, Katsambas A. The microbiome and acne: perspectives for treatment. Dermatol Ther (Heidelb). 2024;14(1):31-44.
- Dreno B, Gollnick HPM, Kang S, et al. Understanding innate immunity and inflammation in acne: implications for management. J Eur Acad Dermatol Venereol. 2015;29 Suppl 4:3-11.
- Reynolds RV, Yeung H, Cheng CE, et al. Guidelines of care for the management of acne vulgaris. J Am Acad Dermatol. 2024;90(5):1006.e1-1006.e30.
- Diogo MLG, Jorge MFS, Campanha NH. Effect of blue light on acne vulgaris: a systematic review. Sensors (Basel). 2021;21(20):6943.
- Hernández-Bule ML, Trillo MÁ, Martínez-García MA, Abreu-Muñoz P. Unlocking the power of light on the skin: a comprehensive review on photobiomodulation. Int J Mol Sci. 2024;25(8):4483.
- Huang YY, Sharma SK, Carroll J, Hamblin MR. Biphasic dose response in low level light therapy: an update. Dose Response. 2011;9(4):602-618.