Post inflammatory erythema (PIE) is a relatively new term used to describe the erythema (redness) that occurs after inflammatory acne. It is considered a form of acne scarring but is different from post-inflammatory hyperpigmentation (PIH), atrophic scars, and hypertrophic scars [1].

Related Reading: Topical Treatments for Post Inflammatory Erythema

Acne and Post Inflammatory Erythema

Acne is caused by multiple overlapping factors and is primarily an inflammatory disease [2]. When a hair follicle (pore) becomes clogged, oil accumulates inside which provides an ideal breeding ground for the p-acnes bacteria. This causes in an immune response and results in inflammation.

Inflammation begins with the clogged pore, continues throughout the acne lesions life-cycle, and remains even after the acne lesion has cleared. Post-acne inflammation is visible in individuals with dark skin as brown marks (hyperpigmentation) and in individuals with fair skin as red marks (erythema) [2][3].

It is thought that both PIE and PIH may be partly due to the slow break-down of the non-surviving p-acnes bacteria in the hair follicle [4]. Additionally, PIE is a result of the blood vessel dilation associated with wound-healing. The appearance of which is worsened by the fact that the skin is thinner during the healing process [1].

Treatment Options for Post Inflammatory Erythema

Vascular Lasers

There are a number of different vascular lasers available to treat post inflammatory erythema. Lasers work by ‘thermolysis’, which is where a substance is broken down by heat. Vascular lasers use ‘selective thermolysis’ to destroy blood vessels in the dermis [5].

In other words, lasers penetrate the skin and heat the dermal layers which causes a healing response. In the case of vascular lasers, the small blood vessels in the skin are heated which destroys the vessel walls and coagulates the blood inside. The body can then break down the old coagulated blood and absorb it back into the bloodstream where it can eventually be excreted. The healing process here is similar to that of a bruise.

Two selective vascular lasers that work well for PIE are the Pulse-Dye Laser (PDL) and the potassium titanyl phosphate (KTP) laser. In fact, PDL is considered the gold standard for treating post-inflammatory erythema [6]. Both lasers target oxygenated haemoglobin (oxyhaemoglobin), which is the substance that gives blood its bright red colour. Oxyhaemoglobin absorbs light in the yellow and green range, especially at wavelengths of 418nanometers(nm), 542nm, and 577nm [6].

Pulsed-Dye Laser (PDL)

As mentioned before, PDL is considered the gold-standard treatment for post-inflammatory erythema. PDL has a wavelength of 585nm. Although, there is also a long-pulsed PDL that has a wavelength between 595nm and 600nm and comes with less risk of bruising as it heats blood vessels slowly [7].

In one study, both scarring and the redness associated with scarring were improved by 68% after one or two treatments with PDL [6]. A more recent study also found improvements in post inflammatory erythema after PDL with 75% of patients rating there results as either good or excellent [8].

Two sessions of a long-pulse PDL (595nm; V-beam laser) spaced four weeks apart improved PIE in 90% of patients with the number of lesions decreasing by 24.9% after the first session and by 57.6% after the second session [9].

As well as treating post-inflammatory erythema, PDL can also encourage collagen production. Although the heat from the laser is targeted at blood vessels, it also diffuses into the surrounding dermal tissue which boosts collagen production [10]. This means that PDL can help improve the appearance of indented scars. In fact, one study reported a 47.8% reduction in the depth of acne scars [11].

Potassium Titanyl Phosphate (KTP) Laser

The KTP laser has a wavelength of 532nm which enables it to target oxyhaemoglobin in the same way PDL does. In one study, the KTP laser performed equally as well as 595nm PDL at reducing erythema in surgical scars [12].

The KTP laser only heats the upper layer of the dermis, which means it can treat post inflammatory erythema without affecting collagen production [13]. This makes it more useful for treating residual redness from blood vessels closer to the surface of the skin [14].

In addition to treating post-inflammatory erythema, the KTP laser can treat active inflammatory acne. This is because the 532nm wavelength is absorbed by the porphyrins that are produced by p-acnes bacteria. The heat from the laser destroys the porphyrins which subsequently damages the p-acnes bacteria [15].

Other Lasers For Post Inflammatory Erythema

While PDL and KTP are the most target specific lasers for treating erythema, there are a number of additional laser treatments that can also help.

Nd:YAG Lasers

Nd:YAG lasers have a wavelength of 1064nm and may help treat erythema that is due to dilated blood vessels within the deep dermis. However, post-acne inflammatory erythema is associated more with the superficial blood vessels, so this laser penetrates deeper than necessary [16].

Microsecond-pulsed Nd:YAG lasers (e.g. Laser Genesis) bulk heat the papillary dermis to reduce superficial erythema. As well as reducing erythema, the heat produced by these lasers stimulates collagen production. One benefit of this laser is that it rarely causes bruising and it can be used on all skin types [16].

As Nd:YAG lasers can boost collagen production, they are also effective at treating atrophic acne scars. Additionally, long-pulsed Nd:YAG lasers are able to selectively destroy overactive oil glands with heat and reduce acne inflammation [17].

In fact, in a case report, a single session of Nd:YAG was sufficient enough to treat mild to moderate acne and reduce acne scarring. These were long-term improvements with no reoccurrence of acne when patients were followed-up after a few years. Although, the case report only included four case studies [18].

This research suggests that Nd:YAG laser treatments could be beneficial for post inflammatory erythema patients who are still experiencing regular breakouts.

Intense Pulsed Light (IPL)

Another treatment option is intense pulsed light (IPL). IPL is not a true laser as it has no specific wavelength, instead, it is made up of multiple wavelengths (approx. 500-1200 nm). For this reason, IPL is a bit of a “Jack of all trades, master of none”. In other words, it can treat several conditions at the same time (including erythema, hyperpigmentation, and pore size) but is less effective at treating any one condition [16][19].

IPL treatments can be used to reduce post inflammatory erythema if acne scars are flat but multiple treatments are needed to achieve a satisfactory result [16].

Fractional Lasers

A laser that is commonly used as a frontline treatment for atrophic scars has also demonstrated redness reducing effects. Erbium-doped fractional laser (EDL) has a wavelength of 1550nm and targets the water contained within dermal tissue. As EDL can penetrate approximately 1mm into the skin, it can also destroy blood vessels deeper in the dermis. This can provide some improvement for post inflammatory erythema.

In fact, one case study found improvement in the appearance of erythema after just one treatment with 1550nm fractional EDL [20]. Another study found that 1550nm fractional EDL improved post inflammatory erythema equally as well as 595nm PDL. Furthermore, patients who received the EDL laser were more satisfied with their treatments than those who received PDL. 91.7% of patients were satisfied with EDL treatment compared to 75% of patients with PDL treatment [8].

After 6 months of treatment with 1550nm fractional laser, two patients experienced a 75% improvement in post inflammatory erythema as well as a 51% – 75% improvement in the overall appearance of acne scars [13].

Laser Risk Factors

The most common side-effects associated with lasers are redness, swelling, and changes in skin pigmentation. These side-effects tend to resolve on their own but can last days to months after treatment [21].

There is some level of discomfort or pain associated with laser treatment. For PDL and KTP the discomfort is often described as a sharp flick or pinprick, similar to the sensation of being flicked with an elastic band [22]. For bulk-heating lasers such as the Laser Genesis, the heat produced can cause some discomfort, but this is usually very mild. In contrast, fractional lasers can be quite painful and usually require local anaesthetic in order to make treatments more comfortable.

Bruising

One side-effect particularly associated with vascular lasers, especially PDL and KTP, is bruising, or purpura. In fact, bruising immediately following a KTP or PDL treatment is expected and usually resolves within 7-14 days. The KTP laser generally results in less bruising than the PDL [22].

Skin Pigment Changes

Darkening of skin pigmentation (hyperpigmentation) can occur with PDL and may last up to 6 weeks after treatment. Lightening of skin pigment (hypopigmentation) can occur with both PDL and KTP in 2.2-26% of patients but generally resolves within 3-6 months [22][23].

Care also needs to be taken with IPL treatments to avoid post-inflammatory hypo- and hyperpigmentation in darker skin types [16]. In contrast, the Nd:YAG laser is the least likely to result in hypopigmentation [22].

While temporary hyper- and hypopigmentation are common, permanent skin pigmentation changes are much rarer. Furthermore, the risk of post-inflammatory hyperpigmentation can be reduced with daily sun protection, or better yet, avoidance of sun exposure [22].

Breakouts

Some laser treatments can activate the herpes simplex virus (HSV) and trigger a cold sore. This is particularly the case with fractional lasers where HSV can present in 0.3-2% of cases. For this reason, antiviral prophylaxis should be given to anyone with a history of facial HSV undergoing fractional laser treatment [24].

Fractional lasers can also cause acne to flare up in 2-10% of patients and the development of milia in 19% of patients [23]. For this reason, fractional lasers are best avoided by those with active acne outbreaks.

Complications

Although the rates of reported complications with lasers are low, there are many potential adverse reactions that can occur, even when performed by experienced practitioners. Most problems are due to either poor technique, mechanical issues, or poor patient compliance.

For example, laser treatments administer varying amounts of heat into the dermal tissue and may cause burns, blistering, and scarring. These adverse effects could be caused by inadequate cooling of the skin or energy settings that are too high. They could also be caused by laser malfunction or by patients failing to disclose recent tanning.

Facial Fat Loss

One particularly worrying side-effect of laser treatment is facial fat loss. Because this is a very rare side-effect, patients are rarely informed of the risk before undergoing laser treatment. However, the laser parameters that are used for acne treatments and facial rejuvenation are close to those used in fat reduction. This means that it is entirely possible for lasers to cause facial volume loss [26].

In terms of vascular lasers, facial volume loss has been witnessed as cutaneous depressions or skin indentations. These complications occur as a result of thermal injury and heat diffusion to the tissue surrounding the target vessels. In some cases, this can be avoided by using lower energy settings. However, even with appropriate laser treatment parameters, skin indentations may still occur [27]. Cutaneous depressions most commonly occur in the nasal creases (nasal alae) and can last six to eight months [22].

Skin indentations have been observed after treatment with Nd:YAG lasers and KTP lasers [27], as well as with PDL [22]. However, theoretically, this adverse reaction could occur from any laser that works by thermolysis. Heat exposure can cause an increase in cell death in heated cells as well as non-heated ‘bystander’ cells. This process has been termed the active thermal bystander effect (ATBE) [28].

Related reading: Facial Fat Loss After Radiofrequency Treatments

Lasers in Practice

To summarise, there are a number of laser treatments available to treat post inflammatory erythema. The majority of these are vascular lasers and specifically target blood vessels in the skin. They can help reduce inflammation as well as erythema which means they also improve the appearance of active acne breakouts. Fractional lasers are usually used to improve the textures of acne scars but have shown some benefit in treating post-inflammatory erythema as well. However, fractional lasers are not suitable if you have active acne as they can cause breakouts which would most likely leave you with more PIE.

The majority of vascular lasers can cause bruising and pigment changes, although this is unlikely with Nd:YAG lasers. Any laser or treatment that works by thermolysis carries the risk of facial volume loss or skin depressions as the heat from the laser can diffuse from the target tissue into surrounding tissue. However, this is a very rare side-effect.

Laser treatments are often expensive and require multiple treatments. It is therefore recommended that you treat any active acne before using laser treatments to improve the appearance of PIE.

Non-Laser Treatment Options

There are some non-laser options that can help reduce post-inflammatory erythema. For example, topical green tea has demonstrated an ability to reduce inflammation, redness, and improve the appearance of existing acne.

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