Psoriasis is a chronic inflammatory disease that tends to recur, and inflammation can appear on all skin types, including the scalp, and can also involve finger (toe) nails and joints. The more accepted methods for evaluating the clinical severity of psoriasis include the lesion body surface area evaluation method, the lesion area and severity index, and the investigator’s overall evaluation. The simplest of these is the lesion surface area evaluation method, which means that a lesion surface area of <3% is considered mild, 3% to 10% is considered moderate, and >10% is considered severe, and 1% of the surface area is approximately the area of a single palm of the patient. Moderate to severe plaque psoriasis, arthritic psoriasis (i.e. psoriatic arthritis), pustular psoriasis and erythrodermic psoriasis all require systemic medication. The following is a brief introduction to the commonly used systemic medications. 1.Vitamin A Since the introduction of synthetic vitamin A in 1943, vitamin A and its derivatives have become a new milestone in dermatological treatment. The current systemic treatment of psoriasis is the efficacy of retinoic acid, which regulates the proliferation and differentiation of epidermal cells and the inflammatory process by regulating gene transcription, thus reducing erythema scales and thinning hypertrophic plaques. Indications include pustular psoriasis, erythrodermic psoriasis and moderate-to-severe plaque psoriasis. Common adverse reactions are dry skin, labyrinthitis, alopecia, increased blood lipids and hepatic impairment. All oral retinoids have teratogenic effects and are therefore contraindicated in pregnant women and women who are unable to use contraception for 3 years. Alcohol consumption is prohibited during and 2 months after discontinuation of the drug to prevent the conversion of Aveline into Aveline ester, which prolongs the half-life of the drug and prolongs the accumulation time of the drug in the body. 2, methotrexate Methotrexate is a dihydrofolate reductase inhibitor, which can inhibit DNA synthesis, thereby inhibiting the proliferation of keratinocytes and immunoreactive cells and improving inflammation. 1971, the U.S. FDA approved the drug for the treatment of psoriasis, the indications include pustular psoriasis, erythrodermic psoriasis, arthritic psoriasis and moderate to severe plaque psoriasis. Major adverse reactions include gastrointestinal reactions (loss of appetite, nausea, vomiting, diarrhea, and abdominal pain), hepatic impairment, lung injury, and complete blood cytopenia, and blood and liver function should be checked regularly during administration. Contraindications to the drug include pregnancy and lactation, severe liver disease and alcoholism. The advantage of this drug is that it is inexpensive and can be taken one to three times a week. 3.Biotics Since 2002, when the US FDA approved etanercept for the treatment of arthritic psoriasis, the development of biologics has flourished. The biologics currently listed or to be listed in China include etanercept, infliximab, adalimumab and ustekinumab, all of which are injectable. The most common infectious adverse reactions are upper respiratory tract infections, nasopharyngitis, sinusitis and influenza. The most common non-infectious adverse reactions are local reactions at the injection site, such as erythema, pruritus, pain and swelling, which usually last for 3-5 days. Contraindications include active infection (including tuberculosis), tumors, congestive heart failure, and hypersensitivity to drug components. The advantages of biologics are that they do not require daily dosing (etanercept once or twice a week, infliximab once every 6-8 weeks, adalimumab once every 2 weeks, and ustekinumab once every 12 weeks), and the disadvantages are that they are expensive and serious adverse events (including death) have been reported. 4. Azathioprine Can be used for plaque psoriasis and arthritic psoriasis. Adverse reactions include alopecia, rash, bone marrow suppression (including leukopenia, thrombocytopenia, anemia) and gastrointestinal reactions, damage to sperm and eggs, teratogenic, and carcinogenic with long-term application. 5.Cyclosporine is mainly used for patients with poor results of other traditional treatments. It is usually applied short-term for 2-4 months, and the course of treatment can be repeated at certain intervals for a maximum of 1 year of continuous application, and the application dose (<5 mg/kg/d) of Pico needs to be strictly followed. The main adverse reactions are hypertension, hepatic and renal toxicity, neurological damage, secondary infections, tumors, gastrointestinal reactions, gingival hyperplasia and hirsutism, etc. The severity of adverse reactions is related to the dose and blood concentration. Blood pressure, blood routine and blood creatinine should be monitored during medication. 6.Antibiotics For patients with punctate psoriasis whose onset is related to upper respiratory tract infection, penicillin or erythromycin antibiotics should be systematically applied at the early stage of onset to clear the causative agent of bacterial infection. 7.Chinese medicine The Chinese medical diagnosis of psoriasis includes blood-heat and wind-heat type and blood-stasis and wind-dry type. For blood-heat and wind-powered type, it is advisable to clear heat and detoxify the toxin, cool blood and dispel wind, and commonly used are compound Qing Dai capsule (pill), Yu Jin Yin Qi tablets, Yin Qi Ling, Yin Qi Punch, Ke Yin Wan, Yin Dissipation Granules and Yin Dissipation Tablets. For blood stasis and wind dryness type, it is advisable to activate blood stasis, nourish blood and dispel wind, commonly used in Blood Mansion, blood circulation, moisten dryness and relieve itching, etc. Mono- and mono-prescription Chinese medicines mainly include Leigongteng, Kunming Mountain Begonia, Bai Shao total glucoside, Glycyrrhizin, Glycyrrhizic acid and Psoralen. During the use of all herbal medicines, blood and urine routine and liver and kidney functions need to be strictly monitored. In conclusion, like topical medications, there are various options for psoriasis systemic medications, which need to be applied under the guidance and monitoring of a doctor. Patients are reminded that although psoriasis systemic medication has developed rapidly in recent years, patients with severe psoriasis still have the possibility of relapse after stopping treatment.