What is psoriasis?
Psoriasis is a skin condition that causes red, scaly plaques, which may or may not be itchy. A key feature is the excessive buildup of scale. Commonly affected sites include the scalp, elbows, knees and lower back, although it can appear anywhere. Some people develop thick scaling on the palms and soles, or nail changes such as thickening, lifting from the nail bed, or a rough distorted surface.
In some cases, psoriasis is linked to arthritis (“psoriatic arthritis”), which can cause painful swelling of the fingers, toes or lower back.
Who gets psoriasis?
Psoriasis is a common skin condition affecting 2-4% of the population, across all ages, genders and ethnicities. While it can begin at any time, it most often starts between the ages of 20 and 40. The condition tends to be less common in sunnier climates, as sunlight can help clear the rash.
What causes Psoriasis?
Psoriasis is an inflammatory condition in which certain immune cells mistakenly enter the skin’s upper layers, causing redness, scaling, and sometimes itch. These cells are not meant to be there, as there is no infection or other reason for them to appear. The exact cause is unknown, but research suggests a complex interplay between genetics, the immune system, and environmental factors. Psoriasis is also now understood to be associated with inflammation inside the body.
Genetics
Psoriasis is not caused by a single gene but by a combination of genetic factors. Each person with psoriasis has a different mix of genes that increases their susceptibility. Although psoriasis can run in families, this occurs in only about 20% of cases.
Immune system dysfunction
People with psoriasis do not have a “weak” immune system. Instead, a small part of the immune system is overactive, driving inflammation in the skin.
Environmental triggers and Lifestyle factors
In those who are genetically predisposed, psoriasis may be triggered by external factors. Stress is the most common trigger. Infections such as a streptococcal sore throat can cause a sudden outbreak of small, scattered spots (known as guttate psoriasis). New plaques may also appear where the skin is damaged, such as after a cut or abrasion.
Smoking can worsen certain types of psoriasis, particularly those affecting the palms and soles that feature white pustules. Being overweight or obese is another risk factor, as excess weight can activate the immune system. Severe psoriasis is often linked with “metabolic syndrome” (a combination of obesity, high blood pressure, raised cholesterol, and pre-diabetes). Addressing these lifestyle factors can help improve psoriasis, even without medication. Alcohol may also aggravate some forms of the condition.
Treatment options for psoriasis
General Measures
- Quit smoking
- Limit alcohol intake
- Manage stress
- Maintain a healthy weight and exercise regularly
Topical Therapy
- Corticosteroids with or without calcipotriol (a form of vitamin D)
- Compounded creams containing salicylic acid, tar, or dithranol
- Tar shampoos for scalp involvement
UV Phototherapy
- Uses a specific form of UVB light, delivered in dermatology clinics through light cabinets
- Typically required 2–3 times per week for at least 20 sessions
- The goal is to clear the skin initially, then to consider a lower dose or frequency to reduce the chance of psoriasis returning
Oral Medications
These treatments dampen or modify the overactive immune response in psoriasis (except acitretin, a vitamin A–based medicine that reduces excessive scaling):
- Methotrexate
- Ciclosporin
- Acitretin
- Apremilast
- Deucravacitinib
Injectable Medications (“Biologics”)
These newer therapies specifically target the overactive part of the immune system in psoriasis. They are injected under the skin (abdomen or thigh) every 1–3 months. Biologics are generally very effective, well tolerated, and can also help manage psoriatic arthritis.
- IL-23 Inhibitors: Guselkumab, Tildrakizumab, Risankizumab, Ustekinumab
- IL-17 Inhibitors: Ixekizumab, Secukinumab, Bimekizumab
- TNF-alpha Inhibitors: Adalimumab, Etanercept, Infliximab
What is the outcome of psoriasis?
Psoriasis can range from mild to severe. Early onset (such as in childhood) and more extensive disease are more likely to persist lifelong, while milder forms may improve, recur, or sometimes disappear. With newer treatments, even severe psoriasis can often be brought into long-term remission, meaning the skin clears completely, sometimes without ongoing medication, although relapses remain possible.