Information for the public

Medical terms explained

Calcineurin inhibitors

Calcineurin inhibitors are drugs that reduce the activity of the immune system and help to reduce inflammation.

Coal tar preparations

Coal tar preparations can reduce scales, inflammation and itchiness. They are available in various formulations, such as lotions, creams, shampoos and products for use in the bath or shower.

Deep vein thrombosis

Deep vein thrombosis is a condition that occurs when a blood clot forms deep inside a vein, often in the leg.

Difficult-to-treat psoriasis

Difficult-to-treat psoriasis occurs on areas of the body such as the face, genitals, scalp, palms of the hands, soles of the feet and in the body creases (also called 'flexures') for example the armpits and under the breasts. Psoriasis in these areas can be difficult to treat completely and because the condition is visible, it can have a greater impact on the person.


Dithranol is a topical medication that slows the production of skin cells. It is often used for 'short-contact' treatment, which means that it is applied for short period of time then washed off or removed with oil. It can cause burning or irritation of normal skin so is only applied to the psoriasis plaques. It is also messy to use and can cause staining.


Erythroderma is a rare form of psoriasis that affects nearly all the skin on the body and can cause intense itching or burning. It can lead to more serious illness, sometimes requiring hospital admission.


Flexures are the creases and folds of the body, such as the armpits, groin and the skin between the buttocks and under the breasts.

Generalised pustular psoriasis

Generalised pustular psoriasis is a type of pustular psoriasis, in which blisters are widespread on the body and can lead to more serious illness. It is not contagious and the blisters are not infected.

Guttate psoriasis

Guttate psoriasis (sometimes referred to as 'raindrop psoriasis') is a form of psoriasis in which small red spots occur over the body, arms and legs. It is more common in children and young people, and can be triggered by a type of throat infection called a streptococcal throat infection. This type of psoriasis may not be long lasting.

Nail psoriasis

Nail psoriasis affects the nails, which develop tiny dents, ridges or pits, become discoloured and grow abnormally, and sometimes separate from the skin and crumble.

Palmoplantar pustulosis

Palmoplantar pustulosis is a type of pustular psoriasis that occurs on the palms of the hands and soles of the feet.

Plaque psoriasis

Plaque psoriasis is the most common form of psoriasis. Raised, red, plaques typically occur on the elbows, knees, scalp and lower back, but it can be more widespread.

Psoriatic arthritis

Psoriatic arthritis is a type of arthritis with swelling, pain and stiffness of one or more joints which may occur in people with psoriasis and needs diagnosing by a rheumatologist.

Pustular psoriasis

Pustular psoriasis is a rare form of psoriasis in which pus-filled blisters appear on the skin. It is not infectious and the pus is not a sign of infection.


A rheumatologist is a doctor who specialises in diagnosing and treating arthritis and diseases related to the joints, muscles and bones.

Scalp psoriasis

Scalp psoriasis is a form of psoriasis in which dry, flaky plaques occur on the scalp, hairline, forehead and inside and around ears.


A specialist is a doctor working in an outpatient dermatology clinic that may be able to offer you additional treatment options.

Specialist nurse

A specialist nurse is an experienced nurse who specialises in working with people with skin conditions.

Systemic biological therapy

Systemic biological therapy is a type of systemic treatment given by injections that is used to treat severe psoriasis or psoriasis that has not responded to other treatments. Systemic biological therapy targets specific parts of the immune system, and includes adalimumab, etanercept, infliximab and ustekinumab.

Systemic non-biological therapy

Systemic non-biological therapy is a type of systemic treatment that includes drugs methotrexate, ciclosporin and acitretin.

Systemic treatment

Systemic treatment means tablets or injections that work throughout the entire body. There are 2 sorts of systemic treatment known as systemic non-biological therapy and systemic biological therapy.

Topical corticosteroids

Topical corticosteroids are topical treatments that reduce inflammation. This slows the production of skin cells and helps reduce itching. They usually come as creams and ointments but are also available as a mousse or shampoo for use on the scalp. Topical corticosteroids are normally used once or twice a day. Topical corticosteroids vary in strength; they can be mild, moderate, potent and very potent.

Vitamin D preparations

Vitamin D preparations slow the production of skin cells and reduce inflammation. They are available as lotions, ointments and scalp solutions and gels. Depending on the product, they can be used once or twice a day.

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