Nummular (discoid) eczema: symptoms, triggers and treatment

Eczema, also called dermatitis, describes conditions in which the outer layer of the skin is inflamed. The British Association of Dermatologists (BAD) explains that discoid eczema is a distinctive type that differs from other types in having characteristic round or oval red patches. “Nummular” means coin-shaped and “discoid” means disc-shaped, which is why the two names are used interchangeably.

BAD says it can occur at any age but is seen more frequently in adults, and is slightly more common in adult men than in women. The NHS notes that it does not usually affect the face or scalp.

The NHS describes the first sign as usually a group of small spots or bumps that quickly join up to form larger patches, from a few millimetres to several centimetres. On lighter skin the patches are pink or red; on darker skin they can be dark brown or paler than the skin around them. Initially the patches are often swollen, blistered and ooze fluid, and they tend to be very itchy, particularly at night. Over time they may become dry, crusty, cracked and flaky.

BAD adds that patches often appear symmetrically, for example on both arms or legs, spread gradually over weeks to months, and are mostly 1 to 3 cm across. You may have one patch, but most people get several, and the skin between them is often dry. After clearing, people with darker skin may notice light or dark marks that persist for months.

• Coin-shaped patches that are intensely itchy, often worse at night.

• Weeping, crusting or blistering early on; dry, scaly or cracked later.

• Patches mostly on the arms and legs and body, rarely the face or scalp.

• Patches that return in the same place.

The NHS advises seeing a pharmacist or GP if you think you may have discoid eczema, as they can recommend a suitable treatment. You should also seek medical advice if you think your skin may be infected.

Signs of infection listed by the NHS include patches oozing a lot of fluid, a yellow crust developing, the skin around becoming hot, swollen and tender or painful, feeling sick, feeling hot, cold or shivery, and feeling unwell. You may need an antibiotic cream or, in severe cases, tablets or capsules.

The NHS says the cause of discoid eczema is unknown, although it may happen as a result of having particularly dry skin, which cannot provide an effective barrier against substances such as soap that come into contact with it. Contact dermatitis may have a role, and some people also have a history of atopic eczema. Unlike atopic eczema, BAD says discoid eczema is not hereditary.

Possible triggers named by the NHS include a minor skin injury such as an insect bite or a burn, and some medicines, though it advises not to stop any prescribed medicine without talking to the prescriber. BAD adds that it can arise in old scars or damaged skin and be worsened by heat, sweating, scratching, local infection and dryness. The NHS says dry environments and cold climates can make it worse, while sunny or humid environments may make it better.

The NHS says a GP should usually be able to make a diagnosis just by examining the affected skin, and may ask questions or arrange tests to rule out other conditions. BAD says the typical round or oval appearance is usually enough, but it is sometimes misdiagnosed as a fungal infection.

Tests listed by BAD that may sometimes be needed include a skin biopsy, patch tests to identify allergic contact dermatitis, skin scrapings to look for fungus, and swabs to check for bacterial infection. The NHS says a GP may refer you to a dermatologist if they are unsure of the diagnosis or if you need a patch test.

Treatment aims to relieve symptoms and keep the condition under control. The NHS lists emollients, topical corticosteroids and antihistamines to reduce itching, plus avoiding irritating chemicals in soaps, detergents, bubble baths and shower gels.

BAD gives more detail, summarised below. It says mild topical steroids are not usually strong enough for inflamed active disease, and that treatment should be restarted at the first sign of recurrence.

BAD says discoid eczema can persist for months or years, often worsening and seemingly improving, and may come back at the same sites each time, including when treatments are stopped too soon. The NHS says occasionally the skin can be left permanently discoloured after the condition has cleared.

Practical measures are the same as for other eczema: avoid irritants, use an emollient daily, and keep to the treatment plan. BAD points to the National Eczema Society as a source of support. BAD also cautions that emollients can catch fire more easily when in contact with dressings, clothing or bed linen, so take care near naked flames and cigarettes.

Most people are diagnosed and treated in primary care, with pharmacists and GPs able to start emollients and steroid treatment. Referral to an NHS dermatologist is usually reserved for unclear diagnoses, patch testing or persistent disease.

Some people choose to see a private dermatologist for faster access or when the condition is not settling. The treatments available are largely the same as those described by BAD, and the main differences are waiting time and cost. Whichever route you use, ask for a written plan that explains how strong each treatment is and when to restart it.