People who get psoriasis usually have one or more person in their family who has psoriasis. Not everyone who has a family member with psoriasis will get psoriasis.

What causes psoriasis?

  • Psoriasis is not contagious.You cannot get psoriasis from touching someone who has psoriasis.You cannot get psoriasis from swimming in the same pool or having sex.
  • Scientists have learned that a person’s immune system and genes play important roles. It seems that many genes must interact to cause psoriasis.
  • Scientists also know that not everyone who inherits the genes for psoriasis will get psoriasis. It seems that a person must inherit the “right” mix of genes. Then the person must be exposed to a trigger.

Many people say that their psoriasis began after they experienced one of these common psoriasis triggers:

  • A stressful event
  • Strep throat
  • Taking certain medicines, such as lithium or medicine to prevent malaria
  • Cold, dry weather
  • A cut, scratch or bad sunburn.

Plaque psoriasis

  • Raised reddish patches on the skin called plaque (plak)
  • Patches may be covered with a silvery-white coating, which dermatologists call scale
  • Patches can appear anywhere on the skin
  • Most patches appear on the knees, elbows, lower back, and scalp
  • Patches can itch
  • Scratching the itchy patches often causes the patches to thicken
  • Patches vary in size and can appear as separate patches or join together to cover a large area
  • Nail problems — pits in the nails, crumbling nail, nail falls off

Guttate psoriasis

  • Small, red spots (usually on the trunk, arms, and legs but can appear on the scalp, face, and ears).
  • Spots can show up all over the skin.
  • Spots often appear after an illness, especially strep throat.
  • Spots may clear up in a few weeks or months without treatment.
  • Spots may appear where the person had plaque psoriasis.

Pustular psoriasis

  • Skin red, swollen, and dotted with pus-filled bumps.
  • Bumps usually appear only on the palms and soles.
  • Soreness and pain where the bumps appear.
  • Pus-filled bumps will dry, and leave behind brown dots and/or scale on the skin.

When pus-filled bumps cover the body, the person also may have:

  • Bright-red skin
  • Been feeling sick and exhausted
  • Fever
  • Chills
  • Severe itching
  • Rapid pulse
  • Loss of appetite
  • Muscle weakness

Inverse psoriasis

  • Smooth red patches of skin that look raw.
  • Patches only develop where skin touches skin, such as the armpits, around the groin, genitals, and buttocks. Women can develop a red, raw patch under their breasts.
  • Skin feels very sore where inverse psoriasis appears.

Erythrodermic psoriasis

  • Skin looks like it is burned.
  • Most (or all) of the skin on the body turns bright red.
  • Body cannot maintain its normal temperature of 98.6° F. Person gets very hot or very cold.
  • Heart beats too fast
  • Intense itching
  • Intense pain

If it looks like a person has erythrodermic psoriasis, get the person to a hospital right away. The person’s life may be in danger.