Nummular eczema

The exact cause is not known. It is assumed that bacteria such as staphylococci or streptococci play a role in the development of nummular eczema as evidence of them is frequently found in inflamed focal points. However, the weeping eczema focal points offer a good basis for growth for the pathogens so that they are also found 'accidentally' but cannot be made responsible as the cause. Another theory is that bacterial pathogens or their decomposition products could cause an allergic reaction in the sense of contact eczema. Hence also the name 'microbial eczema'.

It is unclear whether other chronic bacterial infections (e.g. chronic bronchitis) can contribute to the development of nummular eczema. In some cases, the elimination of the chronic infection resulted in the skin lesions healing up; in other cases, it did not.

Sometimes similar skin appearances also appear with neurodermatitis. That is why it should always be clarified whether it could perhaps be neurodermatitis and not nummular eczema.

The search for the triggering factors of nummular eczema is important, because in the event of an underlying allergic reaction the trigger must be eliminated.