Psoriasis is a chronic, inflammatory disease that is commonly seen and is caused by various factors or interplay of factors including the environmental, immunological and genetic. It has a number of variations such as plaque-type, guttate, generalised pustular and erythrodermic. Additionally, about 20-30% patients of Psoriasis develop Psoriatic Arthritis, usually about a decade after the appearance of Psoriasis. 
Psoriasis is not contagious , you can’t get or transmit it by touching someone. Additionally, it is not an outcome of poor personal hygiene.
The scope of this post is dietary considerations for this disease, which I’m going to extend somewhat to the effects of diet, such as weight gain.
Here are three dietary approaches towards the management of psoriasis:
- Lose Weight: A higher BMI is associated with an increased risk of developing Psoriasis in addition to an increase in the severity of the disease. Additionally, severe Psoriasis is associated with an increased risk of cardiovascular issues, which risk would be reduced if the patient’s weight were ideal. Further, obesity could reduce the effectiveness of medication for the treatment of Psoriasis. 
- Eat Heart Healthy, Anti-Inflammatory Food: Psoriasis and heart disease share a common factor – they’re both inflammatory diseases, and patients may benefit from reducing inflammation and increasing heart health. 
- Low Gluten: Research suggests that up to 25% of Psoriasis patients may be gluten sensitive.  After confirming this with appropriate tests, it may be worthwhile going on a low gluten or gluten free diet to alleviate symptoms.
Related: Psoriasis: Foods to Eat and Avoid
- Diet and Psoriasis
- Quality of life in patients with psoriasis