What is psoriasis?

Psoriasis is a chronic skin disorder that produces thick, pink to red, itchy areas of skin covered with white or silvery scales. The rash usually occurs on the scalp, elbows, knees, lower back and genitals, but it can appear anywhere. It can also affect the fingernails.

Psoriasis usually begins in early adulthood but it can start later in life. The rash can heal and come back throughout a person’s life. Psoriasis is not contagious and does not spread from person to person. In most people, the rash is limited to a few patches of skin. In severe cases, it can cover large areas of the body.

How does the rash start?

Psoriasis starts as small red bumps that grow in size, on top of which scale forms. These surface scales shed easily, but scales below them stick together. When scratched, the lower scales may tear away from the skin, causing pinpoint bleeding. As the rash grows larger, “plaque” lesions can form.

What are less common forms of psoriasis?

Inverse psoriasis - Psoriasis found in skin folds. This form may present as thin pink plaques without scale.

Guttate psoriasis - Small, red, drop-shaped, scaly spots in children and young adults that often appear after a sore throat caused by a streptococcal infection.

Pustular psoriasis - Small, pus-filled bumps appear on the usual red patches or plaques.

Sebopsoriasis - Typically located on the face and scalp, this form is made of red bumps and plaques with greasy yellow scale. This is an overlap between psoriasis and seborrheic dermatitis.

What causes psoriasis?

The cause of psoriasis is unknown. The condition tends to run in families, so it may be passed on to children by parents. Psoriasis is related to a problem of new skin cells developing too quickly. Normally, skin cells are replaced every 28 to 30 days. In psoriasis, new cells grow and move to the surface of the skin every three to four days. The build up of old cells being replaced by new cells creates the hallmark silvery scales of psoriasis.

What causes psoriasis outbreaks?

No one knows what causes psoriasis outbreaks. How serious and how often outbreaks happen varies with each person. Outbreaks may be triggered by:

  • Skin injury (for example, cuts, scrapes or surgery)
  • Emotional stress
  • Streptococcal and other infections
  • Certain prescription medicines (for example, lithium, and certain beta blockers)

What are the symptoms of psoriasis?

As well as the symptoms described above, the rash can be associated with:

  • Itching
  • Dry and cracked skin
  • Scaly scalp
  • Skin pain
  • Pitted, cracked, or crumbly nails
  • Joint pain

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