Atopic eczema is a skin disease that is genetically determined. This is why it is referred to as constitutional eczema.
Summary
The figures speak for themselves: in homozygote twins ("real" twins, who have the same genetic makeup), the disease affects both individuals in 80% of cases. In the same way, hereditary transmission of the disease is around 50% if only one parent has it and 80% if both parents have it: this is called hereditary eczema.
Generally speaking, this is atopy, meaning a hereditary predisposition for developing excessive reactions due to common environmental allergens, which is transferred from generation to generation. It therefore isn't rare to hear that Grandpa Andrew had asthma or Uncle Paul had allergic rhinitis (also known as hay fever).
However, it is important to emphasize that these figures do not reach 100%. Atopic eczema depends both on genes and on several environmental factors.
In the case of eczema, two types of genes are involved: some are involved in the formation of the skin barrier and others regulate the immune system. A mutation on a protein gene called filaggrin is very often discussed since it was highlighted in 2006, but it is found in only 30% of patients and thus remains insufficient to explain all cases of atopic dermatitis. Inversely, an individual can be a carrier of the mutation and never have eczema.
During pregnancy, parents with eczema are often afraid of transferring this skin disease to their child: of course they would prefer to prevent them from having the same difficulties as they do...If ever eczema occurs, parents must not blame themselves, but should consider that they are in a good position to be of help to their child and offer them the best of care.
