The common causes of redness and swelling on the face after fractional laser treatment are laser micro damage, allergic dermatitis and folliculitis. 1. Laser tiny damage: Fractional laser is a treatment method that causes tiny damage to the skin by laser, thus stripping the epidermis and promoting the rearrangement of collagen fibers in the dermis at the same time, in the process of treatment, due to the fact that the laser will cause certain damages to the epidermis and dermis, temporary redness and swelling can occur. 2. Allergic dermatitis: If the allergic person has an allergic reaction to the skin of the face after the fractional laser, the permeability of the facial capillaries will increase, thus causing redness and swelling. 3. Folliculitis: If after fractional laser, improper care, facial skin is infected by bacteria and other pathogens causing folliculitis, the skin around the hair follicle will appear local capillary expansion, so the face will be red and swollen. If the face is red and swollen after doing fractional laser, you should go to the regular hospital in time to find out the cause of the disease and choose the suitable treatment under the guidance of professional doctors.