Psoriasis

Psoriasis is a chronic, immune-mediated skin condition in which the immune system mistakenly triggers inflammation in the skin, causing skin cells to be produced far faster than normal. Instead of the usual monthly renewal cycle, new skin cells form and rise to the surface in as little as three to four days, faster than old cells can shed. This build-up produces the raised, red, scaly patches (plaques) that are the hallmark of the condition.

Psoriasis is common, affecting roughly 2 to 3% of people worldwide, and while it most often appears on the elbows, knees, scalp and lower back, it can affect any part of the body, including the nails, palms, soles and genital area. It is not contagious — it cannot be spread by skin contact — but it is a lifelong condition that tends to follow a relapsing and remitting course, with flare-ups lasting weeks to months, interspersed with periods of remission where symptoms improve or clear.

Importantly, psoriasis is now understood to be far more than a skin condition. It is a systemic inflammatory disease, meaning the same immune overactivity that affects the skin can also affect the joints, and is linked to a meaningfully higher risk of several other health conditions, including cardiovascular disease and metabolic syndrome. Because of this, and because of the significant emotional and social toll visible skin disease can carry, modern psoriasis care looks well beyond the skin — at joint health, cardiovascular risk, and psychological wellbeing — as part of a single, coordinated treatment plan.

Types of Psoriasis

Psoriasis is not one single condition but a group of related presentations, each with a distinct appearance, common triggers and typical distribution on the body. A person may experience more than one type over their lifetime, and one type can sometimes evolve into another.

Plaque Psoriasis: The most common form, accounting for roughly 80–90% of cases. Presents as well-defined, raised, red or discoloured patches covered with silvery-white scale, typically on the elbows, knees, scalp and lower back.
Guttate Psoriasis: Presents as numerous small, drop-shaped, scaly spots scattered across the trunk and limbs. Often appears suddenly in children and young adults, frequently triggered by a streptococcal throat infection. May resolve on its own or evolve into plaque psoriasis.
Inverse (Flexural) Psoriasis: Appears as smooth, shiny, thin red patches without the typical scale, located in skin folds such as the armpits, groin, under the breasts and around skin creases, where moisture and friction change how plaques present.
Erythrodermic Psoriasis: A rare but severe and potentially life-threatening form in which widespread redness and scaling cover most of the body surface. It can disrupt the skin's ability to regulate temperature and act as a barrier, and requires urgent medical attention.
Pustular Psoriasis: Characterised by white, pus-filled blisters (pustules) surrounded by red skin. May be localised to the palms and soles, or generalised and associated with fever and systemic illness, in which case it is a medical emergency.
Nail Psoriasis: Affects the fingernails and toenails, causing pitting, discolouration, thickening, crumbling or separation of the nail from the nail bed. Can occur alongside any type of skin psoriasis or on its own, and is often linked with psoriatic arthritis.
Scalp Psoriasis: Affects the scalp and hairline with red, scaly patches that can extend onto the forehead, neck and behind the ears, and may be mistaken for severe dandruff or seborrhoeic dermatitis.

Causes of Psoriasis

Psoriasis develops from a combination of genetic predisposition and immune system dysfunction, usually set off by an environmental trigger in someone already predisposed to the condition.

Immune system dysfunction: In psoriasis, T cells — immune cells that normally target infection — become overactive and mistakenly attack healthy skin cells. This triggers a cascade of inflammatory signalling molecules (cytokines), particularly TNF-alpha, interleukin-17 (IL-17) and interleukin-23 (IL-23), which drive inflammation and the rapid overproduction of skin cells. These same cytokines are now the specific targets of the newest generation of psoriasis medications.
Genetics: Psoriasis runs strongly in families. Having one parent with psoriasis increases risk, and having two affected parents increases it further, reflecting the role of multiple genes involved in immune regulation.
Environmental triggers: In someone genetically predisposed, specific triggers can set off a flare or bring on the condition for the first time. Common triggers include infections (particularly streptococcal throat infections, which classically trigger guttate psoriasis), skin injury or trauma (a flare occurring at the site of a cut, scrape or sunburn is known as the Koebner phenomenon), certain medications (such as lithium, some blood pressure medications and antimalarials), stress, cold and dry weather, smoking, and heavy alcohol use.

Symptoms of Psoriasis

Symptoms vary depending on the type and severity of psoriasis, and can range from a few small, easily managed patches to widespread involvement that significantly affects daily life.

Raised, inflamed patches of skin (plaques), often red or purplish on lighter skin and violet, dark brown or grey on deeper skin tones
Silvery-white scales on the surface of plaques, which may flake or shed
Dry, cracked skin that may bleed, particularly if scratched or picked
Itching, burning or soreness around affected areas
Thickened, pitted, ridged or crumbling nails, sometimes with separation from the nail bed
Small, red, drop-shaped spots (in guttate psoriasis)
Joint pain, stiffness and swelling — a possible sign of psoriatic arthritis, which can develop with or, in some cases, before visible skin symptoms

Symptoms typically first appear between the ages of 15 and 35, though psoriasis can begin at any age, including in young children and, less commonly, later in life.

Understanding Severity: More Than Just How Much Skin Is Affected

Doctors classify psoriasis severity not only by how much of the body surface is affected, but also by how much the condition affects a person's daily life — because a small patch on the face or hands can be far more distressing and disabling than a larger patch somewhere less visible.

Body Surface Area (BSA): Broadly, psoriasis affecting less than 3% of body surface area is considered mild, 3–10% moderate, and more than 10% severe, though involvement of sensitive areas such as the face, scalp, palms, soles or genitals may be treated more intensively regardless of the total area affected.
Psoriasis Area and Severity Index (PASI): A standardised clinical scoring tool that combines the severity of redness, thickness and scaling with the extent of body area involved, giving an overall score used to track response to treatment, particularly for systemic and biologic therapy.
Dermatology Life Quality Index (DLQI): A questionnaire measuring how psoriasis affects daily activities, relationships, work and emotional wellbeing — recognising that quality-of-life impact does not always correlate neatly with the visible extent of skin disease.

The psychological and social burden of psoriasis is well documented and should not be underestimated. Visible plaques, scale and flaking can affect self-esteem, relationships, intimacy, clothing choices and social participation, and rates of anxiety and depression are meaningfully higher among people with psoriasis than the general population. Addressing this burden — through open discussion, counselling where needed, and effective treatment — is considered an integral part of good psoriasis care, not a separate concern.

Associated Conditions and Complications of Psoriasis

Because psoriasis reflects a broader pattern of immune-driven inflammation rather than a purely local skin problem, it is associated with a higher risk of several other health conditions. This is one of the most important — and often underappreciated — aspects of the disease./p>

Psoriatic arthritis: Affects up to 30% of people with psoriasis, sometimes years after skin symptoms begin. Causes joint pain, stiffness and swelling, most often in the fingers, toes, wrists, knees and lower back, and can cause permanent joint damage if left untreated — making early recognition and referral important.
Cardiovascular disease: People with moderate-to-severe psoriasis have a higher risk of heart attack, stroke and other cardiovascular events, thought to be driven by shared inflammatory pathways rather than lifestyle factors alone — meaning cardiovascular risk assessment is now a recommended part of routine psoriasis care.
Metabolic syndrome: Higher rates of obesity, type 2 diabetes, high blood pressure and abnormal cholesterol are seen in people with psoriasis, often clustering together as metabolic syndrome.
Eye conditions: Conditions such as conjunctivitis, blepharitis and, less commonly, uveitis (inflammation inside the eye, which requires urgent treatment to prevent vision loss) occur more frequently in people with psoriasis.
Other inflammatory conditions: Inflammatory bowel disease (Crohn's disease and ulcerative colitis), kidney disease and certain liver conditions are also seen at higher rates in people with psoriasis.
Mental health: Rates of anxiety, depression and reduced quality of life are significantly elevated in people with psoriasis, related both to the visible nature of the disease and to shared inflammatory pathways affecting mood.
Skin colour changes: Temporary lightening or darkening of the skin where plaques have healed (post-inflammatory pigment change), which usually fades over time but can take months.

How Psoriasis is Diagnosed

Clinical History: A discussion of when symptoms began, their pattern and location, any joint symptoms, family history of psoriasis, and possible triggers such as recent infection, stress or new medication.
Physical Examination: A thorough examination of the skin, scalp and nails to identify characteristic plaques, distribution and severity, which is usually sufficient to make the diagnosis in typical cases.
Skin Biopsy: A small sample of skin may be taken and examined under a microscope when the diagnosis is uncertain, or to distinguish psoriasis from other skin conditions with a similar appearance, such as eczema or fungal infection.
Joint Assessment: Screening questions and, where relevant, physical examination or imaging of the joints to check for early signs of psoriatic arthritis, particularly in people with nail involvement, which is strongly associated with joint disease.
Screening for Associated Conditions: Blood pressure, blood glucose and cholesterol screening may be recommended given the higher cardiovascular and metabolic risk associated with moderate-to-severe psoriasis.

Living Well with Psoriasis

Bathe gently: Daily lukewarm (not hot) baths or showers with gentle cleansers, avoiding harsh scrubbing, help remove scale without irritating the skin.
Moisturise consistently: Applying a thick, ointment-based moisturiser daily — and immediately after bathing while skin is still damp — helps reduce dryness, cracking and itching. A humidifier can help in dry indoor air.
Be thoughtful with sun exposure: Brief, controlled sun exposure can improve some plaques, but this should be discussed with a doctor first, as sunburn can trigger new flares (via the Koebner phenomenon) and excessive sun exposure raises skin cancer risk.
Avoid scratching and picking: Keeping nails short and using anti-itch treatments (such as those containing hydrocortisone or salicylic acid) as advised by your doctor can help prevent scratching from triggering new lesions or infection.
Know and manage your triggers: Identifying and, where possible, avoiding personal triggers — such as stress, smoking, heavy alcohol intake, certain medications or skin trauma — can help reduce flare frequency.
Support overall metabolic health: As psoriasis is linked with higher cardiovascular and metabolic risk, a balanced diet, regular exercise and maintaining a healthy weight benefit both overall health and, for some people, psoriasis severity itself.
Prioritise mental health: Given the well-documented psychological impact of psoriasis, connecting with support groups, counselling or mental health professionals is a valid and valuable part of comprehensive care.
Stay engaged with follow-up care: Psoriasis is a fluctuating condition — an approach that works well can stop working over time, and ongoing follow-up allows treatment to be adjusted as needed rather than accepting a flare as inevitable.