The following side effects are expected during the laser treatment course. Contact your doctor if these symptoms are severe and/or do not go away:

How Common (based on clinical studies)

Mild rednessUp to 100% of all users
SwellingUp to 100% of all users
PainUp to 100% of all users
Flare-up of pustular lesionsUp to 33.3% of all users
Pigmentary changesUp to 16.7% of all users
Flare-up of papular lesionsUp to 12.5% of all users
BlistersUp to 4.3% of all users
VesiclesUp to 3.7% of all users
PurpuraUp to 2.4% of all users
Itching Up to 2.4% of all users
Dryness of skinUp to 2.4% of all users
Dryness of lipsUp to 2.4% of all users
Watery eyeUp to 2.4% of all users

Laser treatment may also cause other side effects that are not mentioned here. Contact your doctor if you experience any other troublesome symptoms after laser treatment.

References
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  2. Bernstein EF. Double-pass, low-fluence laser treatment using a large spot-size 1,450 nm laser improves acne. Lasers Surg Med. 41(2), 116-21 (2009). 
  3. Haedersdal M, Togsverd-Bo K, Wiegell SR, Wulf HC. Long-pulsed dye laser versus long-pulsed dye laser-assisted photodynamic therapy for acne vulgaris: A randomized controlled trial. J Am Acad Dermatol. 58(3), 387-94 (2008).
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  8. Seaton ED, Charakida A, Mouser PE, Grace I, Clement RM, Chu AC. Pulsed-dye laser treatment for inflammatory acne vulgaris: randomised controlled trial. Lancet. 362(9393), 1347-52 (2003). 
  9. Voravutinon N, Rojanamatin J, Sadhwani D, Iyengar S, Alam M. A Comparative Split-Face Study Using Different Mild Purpuric and Subpurpuric Fluence Level of 595-nm Pulsed-Dye Laser for Treatment of Moderate to Severe Acne Vulgaris. Dermatol Surg 42(3), 403-9 (2016). 
  10. Wang SQ, Counters JT, Flor ME, Zelickson BD. Treatment of inflammatory facial acne with the 1,450 nm diode laser alone versus microdermabrasion plus the 1,450 nm laser: a randomized, split-face trial. Dermatol Surg. 32(2), 249-55; discussion 255 (2006).
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  12. Jung JY, Choi YS, Yoon MY, Min SU, Suh DH. Comparison of a pulsed dye laser and a combined 585/1,064-nm laser in the treatment of acne vulgaris. Dermatol Surg. 35(8), 1181-7 (2009). 
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