Psoriasis vs eczema: how to tell the two skin conditions apart

Look at the patch and think about the person. Psoriasis is typically a patch of dry, flaky skin with silvery-white scales, often on the elbows, knees or scalp, with symptoms often starting between 15 and 25 or between 50 and 60. Atopic eczema is typically itchy, dry, cracked or scaly skin, commonly in the creases of the elbows and knees, usually starting in babies and young children, in someone who may also have hay fever or asthma or a family history of them.

There is overlap, and some people have unusual presentations. Both can be on the hands and scalp. The NHS describes psoriasis as caused by a problem with the immune system and atopic eczema as linked to family history of eczema, asthma or hay fever. A GP can usually distinguish them by examining the skin, and a dermatologist is involved when the picture is unclear.

The NHS says psoriasis is a common skin condition that causes itchy and painful patches of dry, flaky skin that form what look like silvery-white scales. Patches are usually 1 to 2cm, oval or irregular, and most people get only a few, though some have them across large parts of the body. It is mostly found on the head and behind the ears, chest, tummy and back, bottom, forearms and elbows, and lower legs and knees, and also in skin folds and on the nails, where there may be dents and pits.

It is caused by skin making more skin cells than usual, thought to be a problem with the immune system, and it is more likely if a family member has it. Triggers include stress, alcohol, smoking, obesity, certain medicines, infections, skin injuries and sunlight. The NHS says some people with psoriasis develop psoriatic arthritis, and advises seeing a GP if joint pain, stiffness or swelling keeps coming back.

The NHS says atopic eczema is a common skin condition that causes itchy skin, affects people of all ages but is most common in young children, and cannot be cured but can be managed. It is common on the elbows, knees and hands and, in babies and toddlers, on the face. The skin can be itchy, dry, cracked, crusty, scaly or thickened and may blister or bleed. Symptoms usually start in babies and young children and tend to get better as they get older, with flare-ups and better periods.

The British Association of Dermatologists says about 1 in 5 children in the UK develop eczema, that the main symptom is itching and that a weak skin barrier, linked to a gene called filaggrin in some people, lets irritants and germs in. It often runs in families, especially with asthma or hay fever, and a healthcare professional can usually recognise it by looking at the skin without blood or skin tests. Treatment centres on regular emollients and, when needed, steroid creams.

A few questions help. Did it start in early childhood, and is itch the dominant problem? That favours eczema. Are there well-defined scaly plaques, scalp involvement, nail pitting or a relative with psoriasis? That favours psoriasis. Does it sit in the creases of the elbows and knees? The BAD says that is a common pattern for atopic eczema. Is there joint pain or stiffness? The NHS says that should be mentioned to a GP.

The NHS advises seeing a GP if you have symptoms of either condition or if treatment is not working. For eczema, it advises an urgent GP appointment or NHS 111 if the skin is blistered, crusty, leaking fluid, painful, swollen, warm, suddenly worse or accompanied by fever, as these may signal infection or eczema herpeticum. For psoriasis, it advises calling 999 or going to A&E if the skin quickly turns red with pus-filled bumps that join together, or the feet or fingertips develop yellow-brown, pus-filled patches.