Severity of Psoriasis

The severity of psoriasis is measured with the Psoriasis Area and Severity Index (PASI) score. It is a scale that takes into account the area of lesion coverage (calculated as the percentage of the affected body surface area) as well as plaque appearance (redness, thickness and scaling). A PASI score of:

  • ≤10 suggests mild psoriasis
  • >10 suggests moderate-to-severe psoriasis

A second assessment may also be performed that measures the impact of your psoriasis on your quality of life (called the dermatology life quality index; DLQI). Results are reported on a scale of 0 to 30:

  • 0−1 (no effect)
  • 2−5 (small effect)
  • 6−10 (moderate effect)
  • 11−20 (very large effect)
  • 21−30 (extremely large effect)


Psoriasis is usually classified as mild when you have:

  • a PASI score of ≤10 and Dermatology Life Quality Index (DLQI) ≤10

As the PASI score takes into account both the appearance and the area of the plaques, mild psoriasis could involve slight redness, thickness and/or scaling that covers a large area of your body, or it may involve severe thickness, scaling and/or redness that covers a small area of your body.

Patients with mild psoriasis often feel embarrassed and self-conscious following the initial diagnosis. However, you need to remember that your GP can offer you a lot of options to manage your psoriasis.


Psoriasis is usually described as moderate-to-severe when you have:

  • a PASI score of >10 and/or DLQI >10

As the PASI score takes into account both the appearance and the area of the plaques, moderate-to-severe psoriasis could involve severe redness, thickness and/or scaling that covers the majority of your body, or it may involve moderate redness and thickness covering large areas with severe scaling in just a few places.

  • In some cases of mild psoriasis (PASI ≤10 and DLQI ≤10), certain features may change the classification to moderate-to-severe including:
    • there are areas affected that are visible with clothing on
    • major parts of the scalp are affected
    • the genitals are affected
    • palms of the hand and/or soles of the feet are affected
    • at least two fingernails are separated from the nail bed or deformed
    • itching that leads to scratching
  • Warrants the use of light therapy or systemic treatments
  • Affects your ability to work or your personal life (e.g. you miss work or sometimes avoid social situations because your psoriasis is flaring).

Patients with moderate-to-severe psoriasis may require more than just topical treatments in some cases. If this is the case, remember this is not uncommon and there are several other treatments that may work better for you.

Diagram showing the severity of biologics

This information is intended as a guide to help you understand how severe your psoriasis is. Your GP or dermatologist may be able to give you a more accurate diagnosis and determine the best treatment approach for you. If you don’t already have a dermatologist, your GP will be able to refer you to one.