Nummular eczema, also called nummular dermatitis, is a skin condition that creates coin-shaped skin lesions most frequently on the arms and legs. The lesions can also be found all over or anywhere on the body.
These blemishes are very dry, scaly patches of the skin that become crusty and itchy, and they may ooze fluid. Nummular is a relatively uncommon condition that isn’t contagious in and of itself, but the triggering factor can sometimes be contagious.
I like to explain nummular eczema as a “dry skin tipping point” form of eczema that can sometimes be associated with or exacerbated by colonization or infection with a bacteria called Staph. aureus.
The dry skin tipping point describes people who have dry skin or have entered into a dry environment and the skin just can’t rehydrate itself anymore. The result is nummular eczema. Oftentimes, these people will also be found to have a folliculitis or an overt skin infection or Staph. aureus in their noses.
What Causes Nummular Eczema?
Unfortunately, there is no confirmed cause that induces this condition one hundred percent of the time. Although it has been associated with a history of allergies, dermatitis and asthma, sensitive skin is very typical in those who develop nummular eczema, and can make their condition worse with: temperature fluctuations, increased stress, dry skin and common household items such as soaps and detergents. In general, anything that will dry out the skin can trigger nummular eczema.
The risk of developing nummular eczema is higher for people who:
- Live in cold and dry weather.
- Have naturally dry skin.
- Have edema (swelling of a body part)
- Have poor blood flow.
- Have other forms of eczema and/or dermatitis.
- Have damaged skin.
- Have a bacterial infection of the skin.
Nummular Eczema v. Psoriasis
Nummular eczema and psoriasis often get confused for each other, but there are certainly some differences. Nummular eczema produces a scaly, pink and often oozy circular-shaped patch. It is often preceded by or results in a whitish patch of skin called pityriasis alba. Psoriasis plaques on the other hand, are more rough, pink-red and raised. The scale of psoriasis plaques is more silver-colored.
The distribution of the lesions are also very different. Psoriasis often starts on the knees and elbows and can then proceed to affect any area of the body including the scalp, trunk, lower back, and groin. Nummular dermatitis will often affect anywhere on the body with no rhyme or reason, but usually does affect the upper arms or upper legs.
Unlike nummular eczema, the cause of psoriasis is somewhat understood. It is caused by an immune system malfunction in which skin cell production is greatly accelerated. Psoriasis causes skin cells to become Type A overachievers, which means they grow much faster than normal skin cells.
When an immune system response takes place, a type of white blood cell called T cells attack the area of the psoriasis-affected skin and then builds up underneath as a result of the inflammation. This is what makes psoriasis more thick, red, and raised.
Treating Nummular Eczema
There is no perfect cure for nummular eczema, but all treatment regimens should target repairing and hydrating the skin barrier, inflammation, and the entire body should be examined for a possible site of infection or overgrowth of Staph. aureus.
I have found that the use of hypoallergenic skin barrier optimizing moisturizers are extremely effective in combating nummular eczema in conjunction with a short course of a topical steroid. Sometimes a very potent topical steroid is needed and I have a compounding pharmacist compound this steroid into the skin barrier optimizing moisturizers.
I will also often recommend bleach baths and pH adjustment using a gel that contains dilute vinegar to help discourage the growth of Staph. aureus in these patients as well. Very rarely, I may need to prescribe oral antibiotics, but this is pretty rare.
One very important tid-bit that I am always sure to tell my patients about is the dangers of nose-picking! Twenty-five percent of people carry Staph. aureus in their noses and they don’t even know it. This may be part of the driving factor of nummular eczema, or may make it very easy to transfer Staph. from the nose to the skin. So, keep the fingers out of the nose!
Does It Last Forever?
Fortunately, nummular eczema tends to be a more limited form of eczema. Many individuals with severe lesions experience a clearing up of skin damage and don’t have any long-term issues commonly seen with different forms of eczema.