At least 20 psoriasis patients will be compared to at least 20 participants without psoriasis Bacterial genomic DNA will be extracted from stool samples of participants. The intestinal bacterial populations will be compared in order to examine whether there are differences between the groups.

Intestinal bacterial population has a significant influence on health and sickness conditions. It affects the development and the function of the immune system (Th2, Th1 or Th17) by bacterial protein expression and by the composition of the bacterial population.

Psoriasis is an immune related dermal disease. The trigger for this disease is currently unknown but, it is possible that intestinal bacteria are a factor in its development.

Study design:

Participants will be divided into 3 groups:

• Psoriasis patients treated with topical medications
• Psoriasis patients treated with IV or sub-cutaneous medications (e.g biological medications)
• Healthy participants (control group) Bacterial genomic DNA will be extracted from stool samples of participants. The intestinal bacterial populations will be compared in order to examine whether there are differences between the groups.

Inclusion Criteria:

• Dermal psoriasis patients diagnosed by a dermatologist.

Exclusion Criteria:

• Treatment with antibiotics or probiotics within the prior 3 months.
• incapable of signing an inform concent.

Both psoriasis patients and healthy participants (as a control group) will be recruited for the study.