The terms ‘eczema’ and ‘dermatitis’, which are often used interchangeably, describe a group of medical conditions where the skin is irritated, itchy, and inflamed.1,2

Eczema is usually used in the context of the dry, itchy, irritated, cracked skin seen in atopic dermatitis, but other commonly experienced forms of eczema/dermatitis include:3,4

·       contact

·       adult seborrhoeic

·       infantile seborrhoeic (including cradle cap)

·       discoid or nummular

·       pompholyx or dyshidrotic

·       asteatotic or xerotic, also known as ‘eczema cracquelée’

·       varicose, also known as gravitational, stasis or venous eczema/dermatitis.

Eczema herpeticum is a condition where a herpes simplex virus infection develops beyond a normal cold sore into a serious infected rash requiring urgent referral.3

The pathophysiology of eczema/dermatitis is not fully understood, but allergic and immune response, genetics, environmental factors, infection, age, gender and activity can all play a role. Some factors are more prevalent depending on the type of eczema.

Atopy is the predisposition to developing allergic hypersensitivity reactions. People with atopic dermatitis, where there is an association with immunoglobulin E (IgE) levels, often have comorbidities such as asthma or allergies such as hayfever.5

A number of gene mutations are implicated in atopic dermatitis, with some overlap in the gene mutations linked to asthma and the gene regions on chromosomes associated with psoriasis. Environmental factors further influence how the condition progresses from genetic susceptibility through immunomodulation to dermal hyper-reactivity and the manifestation of eczema.

One of the more widely studied skin barrier ‘loss-of-function’ gene mutations has been around filaggrin (filament aggregating protein). Filaggrin promotes the epidermal barrier by binding and aggregating keratin in the epidermal layer. A gene mutation causing the scaly skin condition ichthyosis also increases the likelihood of eczema.5,6

With reduced filaggrin, and therefore less keratin protection, eczematous skin is thought to let in more allergens, antigens and chemicals in atopic dermatitis, while at the same time letting out cellular hydration.5