Eczema (dermatitis) is a term used to describe conditions where there is inflammation of skin. There are several types of eczema. Discoid eczema is one type which causes round or oval red patches of inflamed skin. Infection of the inflamed patches is quite common. The cause is uncertain but affected people tend to have generally dry skin. Treatment includes regular use of emollients to moisturise your skin, steroid creams to reduce inflammation and treatment of any infection of the affected skin.
What is discoid eczema and what are the symptoms?
Eczema is also called dermatitis. Dermatitis is a general term which means inflammation of the skin. There are a number of different types of eczema. Discoid eczema is one of these.
Discoid eczema causes round or oval-shaped, red patches of skin on your body. So discoid refers to the disc shape of the eczema patches. Discoid eczema is also called nummular dermatitis. Nummular literally means coin-shaped, another way of describing the shape of the patches of eczema.
Discoid eczema can start as a small group of little blisters or red spots but then develops into a pinky-red, dry and scaly patch of skin. The skin patches are usually very itchy. The itching is often worse at night and can affect your sleep. Some people complain that the skin patches burn or sting.
The skin between the discoid eczema patches looks normal except that, in general, people with discoid eczema have dry skin.
Discoid eczema often starts on the legs. Some people will only have one or two patches of discoid eczema but others may develop many patches. In some people, patches will only be on the legs but discoid eczema can occur anywhere on the body. However, it is uncommon on the face and scalp. It tends to become worse in the winter months in cold, dry climates. Sun tends to improve the symptoms in most people. Because of these features, discoid eczema can be mistaken for psoriasis.
Sometimes the skin patches can clear in the centre, just leaving a ring of eczema (as in the second picture). If this happens, discoid eczema is sometimes mistaken for ringworm. It is quite common for patches of discoid eczema to become infected with germs (bacteria). Signs of infection include increased redness, weeping, or blistering of the skin patch.
What causes discoid eczema?
The exact cause of discoid eczema is uncertain. However, most people with discoid eczema have generally dry skin. One theory is that the dry skin upsets the normal fatty layer within the outer layer of the skin (the epidermis) which usually helps to protect the skin. Because this protection is lost, special proteins that can cause allergy (allergens) can penetrate through the skin. This can lead to an allergic or irritant response in the skin, so leading to the patches of eczema. In fact, some doctors actually consider discoid eczema as a form of adult-onset atopic (allergic) dermatitis.
Sometimes certain medicines can trigger discoid eczema in some people. For example, medicines used to treat hepatitis C infection (called interferon and ribavirin). Insect bites or injury to the skin can also trigger an outbreak of discoid eczema in some people.
Because the fatty, protective layer within the skin is lost, it is thought that some people with discoid eczema may also have an increased risk of developing contact dermatitis. Contact dermatitis is eczema that is caused by your skin reacting to a substance it has come into contact with. Such substances can include nickel in jewellery or belt buckles, cosmetics, preservatives in creams and ointments, additives to leather, etc. See the separate leaflet called Contact Dermatitis for more details.
How common is discoid eczema and who gets it?
Discoid eczema is quite common and probably affects about 2 in 1,000 people. It seems to be more common in men than in women. Discoid eczema can affect men and women of any age but it most commonly affects people aged between 50 and 65. It also affects women between the ages of 15 and 25. It is rare in children.
How is discoid eczema diagnosed?
It is diagnosed by the typical skin appearance. If your doctor is uncertain about the diagnosis then he or she may need to exclude a fungal skin infection. For example, if there has been clearing of the skin rash in the centre (as described above), they may suggest scraping a few skin cells off a skin patch. These can then be sent off to the laboratory to look for a fungal infection. If your doctor is worried that there may be a bacterial infection of a skin patch, they may take a sample (swab). Again, this can be sent to the laboratory to look for this type of infection.
If your doctor feels that you may have contact dermatitis, they may suggest skin patch testing. In this procedure, tiny amounts of up to 25 or more substances are applied as small patches to your skin, usually on your upper back. They are fixed on with non-allergic tape. Some days later, you return to the skin department and the patches are removed. Your skin is examined to see if there is a reaction to any of the tested substances. See the separate leaflet called Patch Testing for Contact Dermatitis for more details.
What is the treatment for discoid eczema?
Treatment is aimed at:
- Restoring fluid to your skin (called rehydration).
- Treating the skin inflammation.
- Also treating any infection that may be present.
Treatment to help reduce itching may also be suggested.
Skin rehydration treatment
This is done by using emollients. Emollients are often called moisturisers. They are lotions, creams, ointments and bath/shower additives which oil your skin to keep it supple and moist. Emollients should be used as soap substitutes when you are washing, as regular soap tends to dry out your skin. Bath or shower twice a day in cool water, followed by application of an emollient.
Regular use of emollients is the most important part of the day-to-day treatment for people with discoid eczema. Emollients prevent your skin from becoming dry and help to protect your skin from irritants. They should be used on all of your skin and not just the areas affected by discoid eczema. It is particularly important to carry on with daily moisturising of your skin even after a flare-up of discoid eczema has healed. This is to help reduce the chance of a further flare-up.
There are many types and brands of emollients, ranging from runny lotions to thick ointments. The difference between lotions, creams and ointments is the proportion of oil (lipid) to water. The lipid content is lowest in lotions, intermediate in creams and highest in ointments. The higher the lipid content, the greasier and stickier it feels and the shinier it looks on the skin. As a general rule, the higher the lipid content (the more greasy and thick the emollient), the better and longer it works but the messier it is to use. See the separate leaflet called Moisturisers for Eczema (Emollients) for more details.
The use of petroleum jelly is sometimes recommended to keep the skin hydrated.
Topical steroids to reduce inflammation
A topical steroid is a steroid cream or ointment that is applied to your skin. In discoid eczema, topical steroids are applied to the skin patches to reduce inflammation. Ointments tend to be better than creams because they tend to hold water in your skin better and form a better protective barrier for your skin.
Do not use the steroid cream or ointment on normal skin. Also, steroids should only be used when discoid eczema has flared up. They should not be used in between times to keep discoid eczema away. This is because long-term steroid cream use can have some effects on your skin, including thinning of your skin. See the separate leaflet called Topical Steroids for Eczema for more details.
Sometimes wet wrap treatments are used with a topical steroid to treat discoid eczema. Your skin is made wet first with lukewarm water so that it is well hydrated. Then, a steroid ointment is applied to the affected areas of skin. Next, damp pyjamas or bandaging are used to seal in the steroid ointment for around one hour. However, do not try such treatments unless advised by your doctor.
In severe cases, steroid tablets taken by mouth or given by injection may be needed to treat discoid eczema.
Note: when using both an emollient and a topical steroid, you should apply the emollient first. Wait 10-15 minutes after applying an emollient before applying a topical steroid. That is, the emollient should be allowed to absorb before a steroid is applied. (The skin should be moist or slightly tacky but not slippery, when applying the steroid.)
Treatment of infection
You may need antibiotic medication if there is bacterial infection of discoid eczema patches. This may be in a cream or tablet form depending on the severity of the infection.
Treatment to reduce itching
Antihistamine tablets may help to reduce itching and may be particularly useful at night when trying to sleep. However, some antihistamines can make you feel drowsy (even the next day). So, you should not drive and you should not operate machinery if they affect you in this way.
Tar preparations may be helpful, especially in areas of skin that have been thickened and scaly for a long time.
Tacrolimus and pimecrolimus are other creams that may be used to help reduce inflammation in some people with discoid eczema. They may be considered in some people if steroid treatment is not working.
Because discoid eczema tends to improve in the sun, ultraviolet (UV) light treatment (phototherapy) can sometimes be helpful as a treatment. The UV radiation helps to reduce the inflammation in the skin. However, care should be taken, as exposure to UV radiation does carry its own risks of skin damage. This includes an increased risk of skin cancers. So, the risks of this type of treatment need to be weighed against the benefits. This type of treatment is usually used if discoid eczema is severe or other treatments have not worked.
Medicines that suppress your immune system may occasionally be needed to treat discoid eczema. They include medicines such as ciclosporin. Again, they are usually only used in severe cases of discoid eczema that are very difficult to treat and have not responded to other treatments.
Are there any possible complications?
As mentioned above, bacterial infection of a patch of discoid eczema can occur and needs to be treated with antibiotics. Also, care should be taken to avoid scratching the itchy patches where possible. If you scratch a skin patch too much, scarring of your skin can occur.
After a discoid eczema skin patch has healed, in many people there will be no residual signs. However, in some people there can be some permanent brown discolouration of the skin in the affected area. In others, the affected area of skin can become paler than the surrounding skin.
What is the outlook for discoid eczema?
Once discoid eczema has been successfully treated, a flare-up can occur again in the future. Therefore, you should take care to keep your skin well hydrated with emollients to try to reduce the chance of future flare-ups. Where possible, you should also try to avoid anything that may have triggered the eczema, such as hot baths or irritating clothing. You might find a humidifier in the room helps to reduce flare-ups. If flare-ups do occur, they often affect the same areas of skin as before.
Further reading and references
Fleming C, Parry E, Forsyth A, et al; Patch testing in discoid eczema. Contact Dermatitis. 1997 May36(5):261-4.
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