Laser complications

moseley-mainLaser complications

Professor Harry Moseley advises how to reduce risk and avoid adverse events with laser treatments, as well as how to deal with them if they arise


When we’re dealing with lasers, we have to take potential complications into account, and know how to deal with them if they arise. We can use the ALARA principle—As Low As Reasonably Achievable. This means that the risk should be as low as reasonably achievable. If you can minimise the risk and it’s not too difficult then that’s the starting point.

I did an analysis of laser accidents a few years ago, and one practitioner using a CO2 laser sustained corneal damage. He claimed that he had worn the goggles, but  an independent examination of the goggles showed no sign of a laser burn. Therefore, my assumption is that goggles were not worn and they did not adopt the ALARA principle. They didn’t keep the risk as low as reasonably achievable, because they didn’t wear their goggles.

When things do go wrong, as sometimes they do, a key question is often asked: was the accident reasonably foreseeable? So let’s just say, yes things can go wrong, but was it predictable? That’s a key element. Applying this to an analysis of an endoscope accident, the endoscope had been flexed through an acute angle and the fibre broke. Would you say that this was reasonably foreseeable? If you bend a fibre through a tight angle, what do you think is going to happen?

If it’s judged as reasonably foreseeable, one key question has been answered. Of course, when things go wrong it may not be the operator’s fault; the equipment can sometimes let us down. We saw one case concerning a filter that had degraded in an IPL—it had degraded to such an extent that there was an excessive amount of UV and lower wavelength blue light emitted. There was therefore a lot of localised disturbance to the skin.

Any undesired effect of a laser is considered a complication, such as purpura following dye laser or erythema. Now you might say, “This happens all the time”. It does, but it is still considered a complication. So virtually every time you use a laser, assuming you do something useful, you will also cause some degree of harm. We have to accept that complications happen and what we have to do is manage them.

Common complications

Hyperpigmentation, which is more common in darker skin types, can last for several months and is more likely in tanned skin. In our clinic, we don’t treat people with tanned skin because the tan will fade. Send them away and bring them back after the tan has faded. It’s an unstable kind of pigmentation and the melanin is in different parts of the epidermis.

Hyperpigmentation can also be caused by excessive cooling. I once treated a patient’s leg veins, had the cold air machine on and suddenly realised I’d “frozen” the skin. You have to be careful when you’re cooling the skin, because you can cause problems by over-cooling. In my case, the effect was quickly noticed and harm was avoided.

Hypopigmentation is also a problem, particularly in darker skins. It’s quite rare but, in our experience, the hypopigmentation does sort itself out—however, it can take several months before things go back to normal.

Apart from scarring, which of course is permanent, most complications aren’t too serious. Some patients can get an allergic reaction to tattoo pigment, which doesn’t just happen when they’re getting the tattoo; it can also happen when you’re removing it with the laser. Releasing the tattoo pigment, particularly with Cinnabar which is a red pigment that contains mercuric sulphide, can cause quite a nasty allergic response.

Purpura generally resolves, but you do have to warn patients in advance. When managing complications, we also have to manage the patient and let them know before we do anything the things that can go wrong. We have a scrapbook that we keep in the clinic, and it shows the good results and the bad results, so they can see exactly what the risks are.

On several occasions, once I’ve gone through the risks, the patient will decide they don’t want the treatment. We don’t charge for consultation, and we’re happy for them to go away and think about it. It’s very important that patients don’t feel like they’re being pushed into a decision, because they’ll hold that against you. You need to make sure that they’re absolutely certain themselves that they want the treatment.

Hair removal can also cause problems. A meta-analysis published in 2009 reviewed 203 studies to work out what can happen and what can’t happen with hair removal. The incidences are quite variable; with the ruby laser, the incidence of hypo- and hyperpigmentation was 3-5% and superficial atrophic scarring was 3% in darker skin types. Most people would consider a 3% risk of scarring to be unacceptably high.

In our experience, hypo- and hyperpigmentation have always been transient, but transient can be up to 18 months. But using the diode laser, our regular laser for hair removal, we have seen very few problems. We do have the usual erythema, and the skin can sometimes look pretty angry for several hours or even a day or two, but we haven’t had any significant problems.

The NdYAG laser is a dangerous beast because you don’t see what’s happening. Anything that you’re doing with the NdYAG laser, whether you are targeting  hair  or vasculature, tends to happen deep within the skin. It’s a very good laser, especially for darker skins or for leg veins, but you have to use it with care and you have to respect it.

Overall, ruby lasers are less well suited to treating skin types four and above, while the alexandrite, diode and NdYAG are fine for four and five. Skin type six can be treated with the NdYAG laser but use with care.

Pulsed dye lasers

There have been two large cohort studies in the late 90s on complications with pulsed dye lasers. They showed there can be pigment changes between 1% and 9% of patients, and scarring in less than 1% or up to 5%. A good study from Salisbury looked at adverse effects when treating port wine stains, showing the overall adverse effect incidence was about 1.4% per treatment.

One of the study conclusions noted that the incidence of adverse effects in children was not any higher than that in adults. They also pointed out that lower legs are always a problem, because the skin is fairly thin on the lower leg, over the shin area.

Another published study looked at complications of laser dermatologic surgery. In relation to the dye laser, they found occasional problems with the cryogen spray. Some dye lasers use a cryogen spray to cool the skin, and there were some faults with the spray’s delivery. There were bubbles in the supply line, which meant the skin didn’t get cooled and they had three patients with atrophic scars.

Many of the complications in this paper came from using the NdYAG laser, including persistant scarring and ulceration. The main problem is that you don’t see immediately what you’re doing. Sometimes you may be tempted to give a second or third shot, but don’t do it.

However, another paper published in 2013 looked at complications in treating dark skins. The lowest incidence of adverse events associated with laser hair removal on darker skin types was achieved with a long pulse NdYAG laser. So for treating dark skins, the NdYAG is the most appropriate.

Pigmented lesions

So can we treat pigmented lesions safely? Almost any Q-switched laser or IPL will treat lentigo. Café au lait can be treated, but they do tend to recur and some of them are resistant to treatment. I don’t see the point of treating freckles—the best thing is to give the patient some sunscreen and advise that they stay out of the sun.

We’ve been treating a patient in our clinic with an epidermal naevus for preventive measures. She thought it was getting bigger, so she came to us and asked if there was anything we could do to help. Because the area is heavily pigmented, we started off using the Q-switched NdYAG laser.

Since the practice of laser treatment is not an exact science, I decided to also try the Q-switched KTP laser. We used the Q-switched NdYAG at one end of the lesion, working from the bottom up, and the Q-switched KTP working from the top down. Both areas have improved a lot, and the lesion has flattened and is breaking up.

However, the area treated with the Q-switched KTP laser is doing much better than the area being treated with the Q-switched NdYAG laser.
Be careful with melasma because of the risk of hyperpigmentation, particularly if there is a dermal component to the pigmentation. If in doubt, don’t treat. For Becker’s Naevus, we just use the hair removal laser and get rid of the hair because the pigment doesn’t shift very easily. The only lesion that I would say is easily treated is the Naevus of Ota or Ito, using Q-switched lasers; they work very well in that case.

Hair growth

What about changes in hair growth? One complication which is now widely recognised is paradoxical hypertrichosis. In other words, we’re trying to improve the situation by removing hair, and we end up causing increased hair growth. It was first reported in treatments using IPL, with increased growth of fine hair in close proximity to treated areas.

A recent review into paradoxical hypertrichosis showed that incidence is anything between 0.6% and 10%—we don’t know the true value because people aren’t really reporting them. The riskdepends on the skin type; there is greater risk of this in darker skinned patients and those with very fine velous hair.

This paradoxical hair growth can occur when you’re using IPL for other conditions, so it’s not just something to warn about when you’re doing hair removal. Another study showed that we can see this complication on tattoo removal and port wine stains.

Contributing factors include areas with fine hair or lighter coloured hair, and darker skin types. The theory is that with this fine hair, the target isn’t quite big enough to be destroyed, but it’s big enough to absorb some of the beam—particularly if the area is near the edge of the beam, the heat seems to stimulate the production of hair.

It can be avoided to a degree. Place cold packs with crushed ice around the treatment area, which reduces the temperature; if there is some stray light, it won’t be enough to stimulate any hair growth. We use this technique in treating ‘at risk’ areas.

Leukotrichia is laser-induced whitening of dark hair, another complication. We actually change the colour of the hair, because we cause a switch-over from eumelanin production to pheomelanin which is the lighter shade of melanin.


A 2009 study reported a series of patients who were being treated between the eyebrows to remove the hair. There is no detail about the laser technique but the patients didn’t seem to have protective eyewear but simply closed their eyes. But when you close your eyes, your eyeball rotates in the socket and you actually look upwards.

You may think that your patient has their eyes closed, so you’re perfectly safe. But remember, if you’re using a YAG laser, or even a diode laser, you’re getting some penetration. The YAG penetrates up to 3 mm, which can be enough for the iris—which is pigmented—to absorb the beam. In this study, the patient’s iris was damaged with adhesion between the front of the lens and the rear of the iris. The condition had still not resolved three months after the incident.

Another study showed melanoma developing in a tattoo during laser removal. There is no suggestion in the paper that the laser caused the melanoma; it’s very clear that while they were doing the tattoo removal, they noticed a dubious pigmented area, had it biopsied, found it was a melanoma and had it excised. But if you are treating any area where there may be dubious brown lesions, and within a tattoo it’s not always easy to see what you’re treating, stay well clear and get a biopsy.

An interesting case that was recently reported involved permanent hair removal with a pulsed dye laser. A young male patient who had received 22 sessions of dye laser as a child, for removal of a port wine stain. Although this produced improvement, his clinician felt they couldn’t progress the treatment any further and that they’d reached a plateau, so he was referred to someone else.

That’s when a particular feature was noticed—an area showing permanent hair removal. This was an area in which the port wine stain had been removed. As a result, the laser beam penetrated deeper into the skin and was absorbed by the vascular plexus at the root of the hair shaft, which is probably why they’ve ended up with unexpected permanent hair removal.

Another recent case involved second degree burns within a tattoo following IPL laser hair removal. The practitioner was carrying out hair removal and didn’t stop when they got to the tattoo. They probably have removed the hair but they’ve also taken away a chunk of the tattoo.

Needless to say, the patient’s not at all happy. Do not go near a tattoo with a hair removal-type device, laser or IPL, otherwise you’re going to end up with quite a mess. Your patient will not be happy and will most likely sue.


We have to understand the degree of complexity that we’re dealing with. We often try to simplify things, but find that some situations are more difficult to predict and there are too many variables. We can end up doing the wrong thing or saying the wrong things, possibly with the best of intentions. So complications are not nice but they shouldn’t stop us using lasers. By taking account of potential complications, we can actually treat patients better.

Professor Harry Moseley is Honorary Professor in the Dermatology Department at the University of Dundee and Head of Scientific Services in the Photobiology Unit, Ninewells Hospital & Medical School, Dundee, UK

Author: bodylanguage

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