It controls genes that affect the immune system or encode skin proteins that are overabundant with psoriasis. PSORS1 is located on chromosome 6 in the MHC, which controls important immune functions. Three genes in the PSORS1 locus have a strong association with psoriasis vulgaris: HLA-C variant HLA-Cw6, which encodes an MHC class I protein; CCHCR1, variant WWC, which encodes a coiled coil protein  overexpressed in psoriatic epidermis; and CDSN, variant allele 5, which encodes corneodesmosin, a protein expressed in the granular and cornified layers of the epidermis and upregulated in psoriasis.Two major immune system genes under investigation are interleukin-12 subunit beta (IL12B) on chromosome 5q, which expresses interleukin-12B; and IL23R on chromosome 1p, which expresses the interleukin-23 receptor, and is involved in T cell differentiation. Interleukin-23 receptor and IL12B have both been strongly linked with psoriasis. T cells are involved in the inflammatory process that leads to psoriasis. These genes are on the pathway that upregulate tumor necrosis factor-α and nuclear factor κB, two genes involved in inflammation. The first gene directly linked to psoriasis was identified as the CARD14 gene located in the PSORS2 locus. A rare mutation in the gene encoding for the CARD14-regulated protein plus an environmental trigger was enough to cause plaque psoriasis (the most common form of psoriasis). Lifestyle
Conditions reported as worsening the disease include chronic infections, stress, and changes in season and climate. Others factors that might worsen the condition include hot water, scratching psoriasis skin lesions, skin dryness, excessive alcohol consumption, cigarette smoking, and obesity.
Due to their similar safety profiles and minimal benefit of dual therapy over monotherapy, corticosteroid monotherapy appears to be an acceptable treatment for short-term treatment.Moisturizers and emollients such as mineral oil, petroleum jelly, calcipotriol, and decubal (an oil-in-water emollient) were found to increase the clearance of psoriatic plaques. Some emollients have been shown to be even more effective at clearing psoriatic plaques when combined with phototherapy. Certain emollients, though, have no impact on psoriasis plaque clearance or may even decrease the clearance achieved with phototherapy, e.g. the emollient salicylic acid is structurally similar to para-aminobenzoic acid, commonly found in sunscreen, and is known to interfere with phototherapy in psoriasis. Coconut oil, when used as an emollient in psoriasis, has been found to decrease plaque clearance with phototherapy. Medicated creams and ointments applied directly to psoriatic plaques can help reduce inflammation, remove built-up scale, reduce skin turnover, and clear affected skin of plaques. Ointment and creams containing coal tar, dithranol, corticosteroids (i.e. desoximetasone), fluocinonide, vitamin D3 analogues (for example, calcipotriol), and retinoids are routinely used. (The use of the finger tip unit may be helpful in guiding how much topical treatment to use. )Vitamin D analogues may be useful with steroids; steroids alone have a higher rate of side effects. Vitamin D analogues may allow less steroids to be used.Another topical therapy used to treat psoriasis is a form of balneotherapy, which involves daily baths in the Dead Sea. This is usually done for four weeks with the benefit attributed to sun exposure and specifically UVB light.