Collateral vessels in cutaneous regions are the channel of

qi

， blood and body fluids transmission among the skin and striae and interstices， and is also the path of pathogens invasion. It is believed that the key pathogenesis of polymorphic light eruption （PLE） was toxins damaging to the skin， in which the cutaneous collaterals fail to nourish， insecurity of the muscle surface as the basis of disease， the pathogens offending

qi

collaterals and heat constraint to toxins as the driving factors， gradually affecting fluid collaterals and dryness-dampness coexist as the middle link， and latent pathogens in blood level and waiting for the opportunity to onset as the final stage. It is proposed that the basic treatment is to resolve toxins and tranquilize collaterals， and the internal and external treatments are combined together. The internal treatment is to resolve toxins， strengthen collaterals， and assist in unblocking the collaterals， and the modified self-prescribed

Wuteng Decoction

（五藤饮） plus

Yigong Powder

（异功散） were selected as the basic formulas， which promotes the discharge of toxin pathogens and strengthens the power of the cutaneous collaterals to protect against pathogens. For external treatment， according to the performance of skin lesions， scraping， tapping with medicinal solution， ointment were selected to drive away pathogens and resolve toxins， and soothe the cutaneous collaterals.

In the early stage， the skin temperature rose with itching， tingling and no rash， scraping with the self-prescribed

Yinhuangcao Clearing Oil

（银黄草清解油） could be used to activate blood and regulate

qi

， relieve heat and resolve toxins； if the lesions showed erythema， pimples， itching， tapping with the self-prescribed

Qian'ai Xunxi Formula

（千艾熏洗方） could be used to diffuse

qi

and fluid， unblock the collaterals and clean toxins； if the skin lesions thickened with scales， the self-prescribed

Yufu Ointment

（愈肤膏） for external application could be used to resolve toxins and activate collaterals， moisten skin and heal up sore.