Based on the theory of "disease involving both dryness and dampness"， this paper systematically elucidates the three-stage dynamic pathogenesis of chronic plaque psoriasis， mutually reinforcing interaction between dryness and dampness initiating the disease co-transformation perpetuating the disease， and turbid toxins forming the latent root. In the progressive stage， dampness exploits dryness to spread and infiltrate， while dryness accumulates and congeals due to dampness， for which it is suggested to resolve dampness and moisten dryness， thereby interrupting their mutual reinforcement， with the use of modified

Yangxue Jiedu Decoction

（养血解毒汤）. In th

e static stage， incessant mutual transformation between dryness and dampness forms an entrenched state of "

yang

constraint-

yin

impairment-collateral obstruction" in local lesions； treatment should be unblocking

yang

to open sweat pores， nourishing

yin

to moisten collaterals， with the use of modified

Mahuang Fuzi Xixin Decoction

（麻黄附子细辛汤） combined with

Yangxue Runfu Beverage

（养血润肤饮）and

Siteng Beverage

（四藤饮） to reverse the disease course. In the resolving stage， phlegm， stasis and turbid toxins lurk within collaterals and sweat pores， forming latent foci that predispose to recurrence； treatment should focus on regulating

qi

and activating blood to expel latent pathogens， using modified

Lipi Formula

（理脾方） combined with

Huoxue Sanyu Decoction

（活血散瘀汤）.