In general, ultraviolet radiation is stronger in summer, which is conducive to psoriasis recovery, so many psoriasis will be good in summer. Psoriasis is heavy in winter and light in summer, because the incidence of psoriasis is higher the further north the colder it is and lower the warmer it is, for a very important reason, namely ultraviolet intensity. Ultraviolet radiation is stronger in summer and has a therapeutic effect on psoriasis, especially the milder sunlight. Because a very important treatment method for psoriasis is phototherapy, but phototherapy treatment is different from outdoor natural light, because phototherapy is specific wavelength ultraviolet light, especially medium-wave ultraviolet light, which has a better therapeutic effect and less side effects. However, another point should be noted at the same time during this season, that is, sun exposure can aggravate psoriasis, especially drippy psoriasis, and new lesions or expansion of primary lesions in the progressive phase, leading to increased inflammation. Patients with progressive psoriasis often experience psoriasis outbreaks if they are suddenly exposed to the sun, i.e., sunlight induced isomorphic reactions. So although psoriasis is generally better in summer and proper sunbathing is beneficial to psoriasis, care must be taken not to expose oneself to the sun.