Stimulus paradoxical of hair with laser

Paradoxical hair growth is defined as the presence of thicker, longer and more abundant hair than before treatment, both in the treated area and in neighboring areas, after the use of laser or any other pulsed light system.

Paradoxical hair growth with laser, more common than it seems

Lorena Acevedo Fonseca, MD

Rotating resident doctor Aesthetic medicine at Unilaser Médica, Universidad del Rosario

Updated by Adrian Rios, 2023

Reactive hair growth to laser is evident after the patient has stopped treatment for more than three months. 

It takes at least two or three sessions to trigger it.

In practice, it can be consulted after a single session.

It is a phenomenon recognized in the medical literature for more than 10 years, reported by several authors with a global incidence of 10% (1-10).

In very dense areas with thick hair such as the armpits or bikini area, it is only noticeable at the periphery or in the more advanced stages of treatment. 

Therefore, paradoxical hair growth by definition is the thickening of thinner hair present in laser hair removal areas.

How can the origin of paradoxical hair stimulation be explained?

One possible explanation is that laser hair removal standardizes the growth phases of all hair follicles, as it is noticeable that the hairs grow back in synchronous periods.

Once a few weeks have passed after they reappear, it can be noticed in advanced stages of the treatment that the quantity remains stable but some hairs could grow longer than before the laser.

In summary, we will have a predominant population of actively growing hairs, which we will call “anagen”

The prolongation of the anagen phase is the essence of the complete result in laser hair removal.

If this were not done, it could happen that some follicles would remain inactive for long periods of time, but this does not happen. 

In fact, it is the involution of the follicle through autophagy, which explains an aesthetic destruction of the follicle. Without scarring. 

Given this situation, the cases that obtain very high reductions, greater than 90%, are those that maintain the results.

The sweet spot of the matter is how to obtain results greater than 90%.

Well, partial damage to the follicle would generate stimulation rather than destruction .

Is paradoxical hair growth after laser reversible?

A recently reported case illustrates the duration of the paradoxical stimulus.

This is a 21-year-old man with white skin, who after 3 sessions in various areas (back and limbs) developed the phenomenon on his back.

The patient was observed for a period of 10 years without further sessions.

Within a decade, it was shown that the phenomenon was reversed after year 7 and remission was confirmed at year 10 (4). This is the first report of a spontaneous remission.

How to treat laser-induced hair growth?

With another paradox: Continue treatment.

As for treatment, a combination of the effects of different types of equipment may be a good solution. 

A good method for evaluating results must also be used to be able to interpret changes in parameters or equipment. 

If the evaluation of results is carried out with sufficient rigor, it will be possible to estimate the fundamental thing, the real decrease in active follicles. To do this, a frequency in the sessions consistent with the findings must be maintained. 

Therefore, a more methodical approach is required to address this condition.

With this, you can choose the moment to start electrolysis, as this will be impractical for very large amounts of hair.

Finally, depending on the case, it is possible to resume waxing and hope that this will reverse the stimuli in a good number of follicles. 

Illustration 2, Image taken from: Alajlan A, Shapiro J, Rivers JK, MacDonald N, Wiggin J, Lui H. Paradoxical hypertrichosis after laser epilation . J Am Acad Dermatol. 2005;53(1):85–88. doi:10.1016/j.jaad.2004.06.054

Illustration 1, Image taken from: Adam Honeybrookb , Tascha Crossinga , Eric Bernsteina , Jason Blooma , and Julie Woodwardc, Long-term outcome of a patient with paradoxical hypertrichosis after laser epilation, JOURNAL OF COSMETIC AND LASER THERAPY 2018, VOL. 20, NO. 3, 179–183, https://doi.org/10.1080/14764172.2017.1383614.

Illustration 3, Image taken from: Desai S, Mahmoud BH, Bhatia AC, Hamzavi IH. Paradoxical hypertrichosis after laser therapy: a review. Dermatol Surg. 2010 Mar;36(3):291-8. doi: 10.1111/j.1524-4725.2009.01433.x. Epub 2010 Jan 19. Review. PMID:20100274

References

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