IPL does not reliably kill hair follicles outright. It damages them with heat, which can prevent regrowth in some follicles, but the effect is better described as long-term hair reduction than permanent removal. The distinction matters: a significant portion of treated hairs will eventually grow back, especially after a single session, because IPL’s broad-spectrum light often fails to destroy the deepest structures responsible for regeneration.
How IPL Damages Hair Follicles
IPL works through a process called selective photothermolysis. The device emits pulses of broad-spectrum light that get absorbed by melanin, the dark pigment in your hair. Once melanin absorbs that light energy, it converts into heat, which can cause enough thermal damage to destroy the follicle from the inside out.
The key word is “can.” A lab study published in the Journal of Dermatological Science examined what actually happens inside follicles after IPL treatment. The pigmented structures, specifically the melanin-rich matrix cells at the base of the follicle and the hair shaft itself, took the most damage. Heat sometimes extended deep enough to injure the dermal papilla, the tiny cluster of cells that feeds the follicle and signals it to grow. But the stem cells responsible for regenerating the follicle were mostly spared. This is why hairs often grow back after treatment: the follicle’s regeneration machinery survives even when its active growth structures are destroyed.
Only high-energy treatment settings caused damage that reached the dermal papilla consistently. Lower settings damaged the hair shaft and surrounding cells but left the deeper structures intact enough to eventually recover.
Why Hair Growth Cycles Limit Results
Your hair doesn’t all grow at the same time. Each follicle cycles independently through an active growth phase (anagen), a transition phase, and a resting phase. IPL only works on hairs in the active growth phase, because that’s when the follicle contains enough melanin to absorb the light and when the hair shaft is still physically connected to the papilla at the follicle’s base.
On the face, roughly 56 to 76 percent of hairs are in the active phase at any given time. On the legs and arms, the percentage is typically lower. This means a single IPL session can only reach a fraction of your total follicles. With correct settings and good timing, each session reduces active hair counts by approximately 20 percent. That’s why a full course of IPL requires 6 to 8 treatments, typically spaced 4 to 6 weeks apart to catch different follicles as they rotate into the growth phase.
Permanent Reduction, Not Permanent Removal
The FDA uses a specific definition for devices in this category: permanent hair reduction means a long-term, stable reduction in the number of hairs regrowing when measured at 6, 9, and 12 months after completing a full treatment course. Notice the phrasing. It’s “reduction,” not “removal.” No IPL device is FDA-cleared for permanent hair removal, because some follicles will always recover and produce new hairs over time.
After a complete course of 6 to 8 sessions, most people see a noticeable and lasting decrease in hair density. But periodic maintenance sessions are usually needed to manage regrowth, particularly in hormonally active areas like the face, underarms, and bikini line where new follicles can be recruited by hormonal signals.
How IPL Compares to Laser
Laser hair removal and IPL both use light energy to heat melanin, but they differ in precision. A laser emits a single, concentrated wavelength that penetrates deeper into the follicle and delivers energy more consistently. IPL uses multiple wavelengths of broad-spectrum light that scatter as they enter the skin. The result: less concentrated energy reaching each individual follicle, shallower penetration, and a higher chance of missing follicles entirely.
In practical terms, laser tends to produce faster results in fewer sessions and is generally considered more effective for long-term hair reduction. IPL often requires more sessions to achieve comparable outcomes. That said, IPL covers a wider treatment area per pulse, which can make sessions quicker for large body areas like the back or legs.
Skin Tone and Hair Color Matter
Because IPL relies on melanin as its target, it works best when there’s a strong contrast between dark hair and lighter skin. The ideal candidate has light skin (Fitzpatrick skin types I through III) with dark, coarse hair.
For people with darker skin tones (Fitzpatrick types IV through VI), IPL carries real risks. The melanin in the skin’s surface layer competes with the melanin in the hair follicle for light absorption. Instead of the energy being directed primarily into the follicle, it gets absorbed by the surrounding skin, which can cause burns, blistering, and lasting discoloration. IPL is generally not recommended for skin types above Fitzpatrick III for this reason. Certain laser systems with longer wavelengths are a safer option for darker skin tones because they can bypass epidermal melanin more effectively.
IPL is also ineffective on blonde, red, grey, or white hair. These hair colors contain little to no melanin, so there’s nothing to absorb the light energy in the first place. The follicle goes completely untreated.
What Happens Inside the Follicle Over Multiple Sessions
The cumulative effect of repeated IPL treatments is what produces visible, lasting results. Each session damages a new batch of follicles that happen to be in the active growth phase. Some of those follicles sustain enough thermal injury to stop producing hair permanently. Others are weakened but not destroyed, producing finer, lighter hairs that are less noticeable. Still others recover fully and will need to be targeted again.
After the first two or three sessions, most people notice that regrowth is slower and patchier. By sessions five through eight, the remaining active hairs are often thinner and lighter. The follicles that do survive tend to produce progressively weaker hairs with each round of treatment, even if they aren’t fully destroyed. This is partly because repeated thermal injury can shrink the follicle and reduce its melanin content over time, making it both less visible and, paradoxically, harder to treat with subsequent sessions since there’s less pigment to absorb the light.
For most people, the realistic outcome of a full IPL course is a 70 to 90 percent reduction in hair density in the treated area, with maintenance sessions once or twice a year to manage the stragglers. Complete, permanent elimination of every follicle in a treated zone is not something IPL consistently delivers.