Is Psoriasis Contagious?
Psoriasis is NOT contagious.
More Info: Psoriasis is not something that you can catch from another person. It is believed that both genetic factors and environment play a role in its development.
Is Psoriasis an Autoimmune Disease?
Psoriasis is considered an autoimmune disease because the immune system appears to attack normal body tissue. Two types of white blood cells, B-cell and T-cell, seem to be malfunctioning in those with psoriasis. Normally these cells would work to protect the body against antigens, but in the case of psoriasis, the B-cells create antibodies that attack normal skin cells, while the T-cells overproduce a protein that turns off the signal controlling skin cell growth. Skin cells begin to turn over quickly and build up causing blood vessels to rush blood to the area causing both the white flaking and swollen redness characteristic of psoriasis. 
How Common Is Psoriasis?
Psoriasis is the most common autoimmune diseases in the United States with approximately 7.5 million or 2.2% of the population affected in the country. Globally, an approximately equal percentage has the condition at 125 million people. Unfortunately, as of April 2010, there is no cure, but thankfully, it is not a contagious disease. 
Is Psoriasis Genetic?
Psoriasis is not contagious but you may be predisposed through genetics. Though scientists have not definitively concluded the exact cause of the condition, they have concluded that it is likely influenced by genetics due to the fact that approximately one-third of psoriasis sufferers have family members who also have the condition.  A child with a parent with psoriasis has a 10% chance that she will have the condition. This number increases significantly to a 50% chance when both parents have it. 
Who Is Most Susceptible to Psoriasis?
Generally, psoriasis first appears to those between the ages of 15 and 25 and affects women and men. In the U.S. psoriasis seems to affect Caucasians more than African Americans at a comparative 2.5% to 1.3%. 
What Are the Symptoms of Psoriasis?
Psoriasis usually affects the hands, face, knees, elbows, and scalp, but it can appear anywhere on the body. It's a "symmetrical" disease, meaning it affects both right and left sides equally and simultaneously. Because of that balanced duality, it's possible the nervous system may be involved via chemical reactions in the nerve synapses.
Depending on the type of psoriasis, exact symptoms can differ. The most common form, however, is plaque psoriasis that presents the most commonly recognize symptoms of red, inflamed skin with waxy plate flakes. 
Other symptoms include:
- Bumps, postules, or lesions (not infectious)
- Small scaly spots (mainly in children)
- Discolored, ridged, thickened nails
- Painful or swollen joints
- Dry, cracked skin that may bleed
No one knows what causes the disease to first appear, but the symptoms can be treated. When treatment is successful, the disease seems to disappear-but it's not gone; it's just in remission. To avoid new episodes or reduce the severity of the condition, sufferers can and should monitor certain environmental or emotional trigger sets:
Stress: Emotional stress elevates the skin temperature and blood pressure, which could lead to "favorable" conditions for psoriasis.
Smoking: Increases stress on the immune system and can elevate blood pressure.
Alcohol: Heavy consumption inflames capillaries and elevates blood pressure.
Certain medications: lithium and high blood pressure medications, to name a few.
Injury: Cuts, scrapes, and other irritations of the skin can trigger episodes, especially if prone to infections, including eczema.