This is an important question but has not been properly studied clinically (to my knowledge). When my research group first developed the Q-switched ruby laser treatment of tattoos in Canniesburn Hospital, Glasgow, in the early 1980s they established that a minimum four-week period was the optimum time between repeat laser sessions.
This became the standard interval time across the planet for many years.
About 10 years later reports that a six-week period yielded ‘better’ results started to arise in a number of countries. After more time, this interval became eight weeks. However, a proper clinical study has not yet been carried out to determine the most appropriate time.
Figure 1: The rate of removal of ‘lasered’ ink appears to increase significantly after phases 1 and 2 of the skin repair process have concluded. At this time the most important immediate phases of the repair process have completed, leaving time and energy for the less important ink removal part.
So, I approached this from a different stance. I considered the skin repair processes and wondered how laser tattoo removal fitted in with these.
I learned that the repair processes can broken down into four main, overlapping phases:
Figure 2: The timeline of the four phases
1 – Haemostasis – this initial phase minimises blood, and other fluid, losses from the skin, with a rapid influx of platelets, cytokines and hormones. Chemokines are released by platelet activation to attract the inflammatory cells. This phase occurs within minutes of the trauma being formed.
2 – Inflammation – Within hours inflammatory cells such as neutrophils, macrophages and lymphocytes debride damaged or injured tissues during this phase; Macrophages appear to be the most important cells in this phase since they phagocytose both the debris and bacteria. They also release substances which stimulate the next phase – proliferation. However, it has not been shown that tattoo ink particles are removed in this early stages of this phase. This phase can last for over three months (see figure 2).
3 – Proliferation – in this phase regrowth of tissues begins including epithelialisation, fibroplasia and the growth of new blood vessels etc. In addition, granulation tissue begins to form to contract the wounded areas with an increase in fibroblast cells leading to the synthesis and deposition of new collagen. This phase typically begins between 3 and 5 days post-trauma and invariably overlaps with the preceding inflammatory phase. However, the collagen synthesis process can continue at a rapid rate for approximately 2 to 4 weeks, after which the rate slows.
4 – Remodelling (or ‘Maturation’) – This phase mostly concerns the replacement of ‘old’ collagen with newly formed collagen. During this phase collagen becomes increasingly organized, with an increase in cross-linking of the fibres. This leads to a much stronger collagen matrix but can often result in scar tissue formation. This phase usually begins around 21 days after the original trauma, and can continue indefinitely! However, a healed wound will only ever reach around 80% of the original tensile strength of the original, unwounded skin!
It is likely that most of the removal of shattered ink particles occurs during this phase, when the ‘important’ stages above have been completed.
For a fuller account of these processes please visit https://emedicine.medscape.com/article/884594-overview#a1.
A laser treatment of a tattoo is essentially a traumatic event, from the perspective of the skin. There is thermal and physical damage as the absorbed laser energy results in rapid heating of the ink particles leading to steam formation, physical expansion of the local tissues (due to tissue water boiling) and a little thermal damage which can result in very localized scar tissue formation. This occurs every time the tattoo is treated. Consequently, the total amount of scar tissue builds up with each treatment. This suggests that fewer treatments will ultimately generate a better overall outcome.
The main purpose of the skin repair process is to repair the damage to the skin and remove any perceived ‘threats’ such as bacteria, toxins and viruses – the actual removal of shattered ink particles is probably a fairly low priority in the overall process, if it not perceived as a threat!
It struck me that we were treating patients too frequently! At four and six week intervals we were creating new trauma around the ink particles, before the skin repair process had even neared completion!
It also occurred to me that the majority of ink removal had probably not been completed either. Anecdotal evidence clearly suggested that leaving longer periods between treatments resulted in more clearance of the ink.
So, I thought about this and figured out a mathematical approach…
When a relatively short interval is left between repeat laser sessions, the total amount of ink removed is correspondingly small. As can be seen in figure 2, all subsequent treatments occur during the early stages of phase 4, before the majority of ink has been removed.
The vertical green bars indicates the amount of ink removed by the time of the next treatments. If my idea is correct, then this is simply because the main removal process has not had sufficient time to occur, leaving behind most of the ink. Subsequent treatments renew the tissue trauma around the ink particles which triggers the whole repair process again, from the start, beginning with another homeostasis phase.
While the above figures are only my idea of what is happening in the skin, they appear to confirm that leaving longer intervals between laser treatment sessions is probably a good idea. Certainly, my own clinical experience has shown that this is the case. In one patient, I left more than year between two sessions – the amount of ink ‘lost’ was very significant.
Every time we hit a tattoo with laser energy, we generate trauma around those ink particles. The skin responds by going into repair mode. To maximise the amount of ink removed between laser sessions, we must allow the skin to do its job to the best of its ability. This means that we need to leave sufficient time for the natural skin repair processes to occur before introducing new ‘trauma’ around the ink (with another laser session).
If we don’t leave enough time then, we are not allowing for a good clearance of the ink, plus we restart the whole repair process. In essence, we will keep the skin in a state of permanent repair!
Figure 6 indicates that a longer interval between laser sessions allows for more ink clearance. While I have no real clinical evidence to back this claim, there does appear to be plenty of anecdotal evidence from various sources which support it. I am keen to collect as much information on this as possible – if you have seen similar results with long intervals between laser sessions, please let me know.
Below are before and after photos of a treatment I carried out on a young sportsman, using a Q-switched Nd:YAG laser at 1064nm and around 5 J/cm2. The final photo shows the result after only four sessions. The shortest interval between session was 9 months, while the longest was 21 months. Such long intervals clearly allowed his skin repair processes to essentially ‘complete’ before subsequent laser treatments. They also appear to have allowed for maximal ink clearance.
Clearly, the ink continued to leave the area during those gaps, even though there were no laser interventions! Click here for a short video of these photos.
So, what is the “optimum” time between laser sessions?
Well, the answer is that there is no one ‘time’ which suits everyone! Just as we don’t all wear the same-sized shoes, the time between treatments depends on the individuals.
Age, smoking, diabetes, state of fitness, diet, skin conditions, underlying conditions and various other issues will determine the skin’s healing rate, and hence, the ink removal rate.
I suggest that laser operators select a suitable time based on all these factors, with a longer interval being applied to those patients with ‘issues’! But I also suggest that routinely leaving longer intervals is a potentially good strategy for everyone!!
To be brutally frank, I think we should leave six months between EVERY laser session. But, this is the real world – that’s never going to happen!!
I have also noticed, through the years, that very athletic, fit people show rapid signs of ink removal – much faster than the average. I’ve also seen that regular swimmers lose ink more rapidly too – although I’m not sure why yet.
In essence, if insufficient time is left between laser sessions, then it might be a case of “2 steps forward, 1 step back…..”
Ciao for now,
PS If you have any good anecdotal information which supports, or negates, my ideas here, please let me know. Especially if you have good photos! Many thanks.