Acne vulgaris is a fluid condition with multimodal aspects- active disease, post-inflammatory hyperpigmentation, erythema and scarring. Sebaceous gland hyperactivity, altered growth and differentiation of hair follicular cells, proliferation of Propionobacterium acnes and inflammation with an immune response are all factors that contribute to the development of acne. The role of energy based devices for acne (Table I) is slowly gaining acceptance among dermatologists. A variety of devices have been developed which address one or more aspects of acne. They are best used in conjunction with topical therapy. This review will summarize the various devices. Recently, a new scale (the Shamban scale) is being developed which will better enable the dermatologist to tailor device treatment appropriately. The scale addresses the multimodal aspect of acne: active disease severity (A), scarring (S), and pigmentation (P). This article will primarily cover the treatment of active acne. A subsequent article will review treatment of acne scarring.

Clinical Considerations
There are numerous instances when energy based devices are appropriate for the treatment of active acne. These include

1.) failure of standardized therapy for acne (such as topical agents and oral antibiotics),

2.)reluctance of patients to take oral antibiotics,

3.) patients who are actively trying to get pregnant or nursing,

4.) failure of systemic therapies such as oral retinoids.

It is very important to stress that to date there have not been any devices that guarantee non-recurrence of acne. However, even with conventional acne therapies (including oral retinoids), maintenance therapies and repeat therapies are the norm, as acne is a fluid and multimodal disease. Best outcomes with energy based devices are achieved in combination with adjuvant medical therapies.

Endogenous Photodynamic Therapy (Blue And Red Light)
Mild to moderate acne has been reported to respond to non-thermal energy based devices—specifically blue and red light sources. The proposed mechanism is photosensitivity of P. acnes with the protoporphyrin IX having absorption peaks at 410, 505, 540, 580 and 630nm wavelengths with the peak absorption at 410nm (blue). The main advantage of this therapy is lack of discomfort and lack of any adverse side effects, such as hyperpigmentation and scarring. The main disadvantage is variability in results and need for multiple/ongoing treatments. Home based devices use lower fluencies in these wavelengths and may be well suited for maintenance therapy.

Pulsed Dye Laser Therapy and Pulsed KTP Laser Therapy
Pulsed dye lasers have been shown to reduce the size of sebaceous glands and improve collateral erythema associated with acne. Coincidental improvement of acne when treating vascular lesions has been noted. The main advantages of this therapy are simultaneous improvement of erythematous and possibly hyperpigmented lesions, especially with the KTP laser. Disadvantages include variability in results, discomfort, bruising, and hyperpigmentation as well as need for multiple treatments.

Photopneumatic Therapy
Photopneumatic therapy combines the delivery of broadband light in the blue/green spectrum with pneumatic energy. This device has the broadest range of FDA clearances for active acne: inflammatory, pustular, and comedonal. The mechanism combines ejection of congested sebum through application of a vacuum and simultaneous delivery of broadband light for P. acnes and pigmented lesions. The main advantages of this therapy (Figure 1) include simultaneous pore cleansing, lack of pain, and improvement of multiple lesions of acne. The main disadvantages include the need for multiple treatments and maintenance.

Radiofrequency
There have been a few reports of using unipolar radiofrequency for the treatment of acne. This has been observed as a side effect when unipolar RF has been used for skin tightening. Simultaneous improvement of scarring and pore size reduction has also been observed. The main advantage of this therapy is potential long-term treatment. The main disadvantage is the associated costs and discomfort.

Exogenous Photodynamic Therapy
Two photosensitizing agents, ALA and MAL, are now available in the United States for photodynamic therapy, with the former having a great deal of experience used off label for the treatment of acne. The presence of protoporphyrin IX has been noted in sebaceous glands, thereby making ALA and MAL good activators with a variety of light sources for the treatment of acne. Light sources that have been used include blue light, pulsed dye laser, intense pulsed light, photopneumatic therapy and red light. Many physicians will often combine light sources (e.g., blue light and intense pulsed light) for optimal effect, although this has yet to be studied systematically. Single treatments often will result in long-term clearance, and even more aggressive lesions such as nodulo-cystic acne may show a response. The main advantages are fewer treatments and activation with a variety of light sources. The main disadvantages are downtime including erythema, edema and discomfort, as well as variability in duration of clearance.

Practical Considerations
The main challenge in dermatologists' adaptation of energy based devices for the treatment of acne includes cost, compliance and standardized protocols. Cost is a huge issue, as many of these treatments are not covered by insurance. However, if one looks at the excessive costs associated with standard acne therapies that do not work, as well as compliance issues, a discussion with the patient may enable them to realize the long-term costs may not be as great.

Another issue is compliance, as with any acne therapy. Most energy-based devices require multiple treatments as well as adjuvant therapies. Therefore it is important to discuss these during the consultation.

The biggest hurdle, despite cost and compliance, is the lack of well controlled double blind studies with energy based devices. Most studies have small cohorts, and many algorithms are anecdotal. Hopefully, as we better understand these devices and their role, we can have more standardized algorithms for better outcomes.

Our approach in using energy based devices as first line therapy is as follows:

1.) patients who are actively trying to get pregnant,

2.) patients who are nursing.

3.) patients who have failed standard topical and systemic therapies, including oral retinoids.

Our approach for the broader acne patient is to introduce energy based devices after they have started a topical regimen that may be suboptimal. Most patients prefer adjuvant laser or light based therapies over oral antibiotics. The simultaneous improvement in appearance-based issues of acne, such as erythematous scars and hyperpigmentation, are also an advantage over standard therapy. One of us (AS) has designed a novel scale,the Shamban scale, which can assist in creating an algorithm for acne based on the presence of acne severity (A), scarring (S), and pigmentation (P). This is being developed to better understand how conventional and energy based acne treatments can be synergistic.

Conclusions
Dermatologists are gradually embracing energybased devices for the treatment of active acne. Practical challenges include cost and compliance. The greatest challenge is the lack of convincing studies. However, it is clearly evident that devices are here to stay and their appropriate use offers an excellent option for the treatment of active acne.