Eczema: The science behind the itch

Anyone with eczema, or atopic dermatitis, will know that the temptation to scratch that itch can be all consuming. Overwhelming. Torturous.

The exact cause and treatment of the burning red skin has evaded scientists and dermatologists over the years. But now, thanks to the deepening of research on the skin microbiome, the secrets of the skin are starting to provide some answers for this chronic skin condition.

Eczema is an inflammatory skin condition characterized by itching red lesions on the skin. Those with eczema often also report dry, sensitive skin, inflammation and skin damage due to the persistent itch. While there are many types of eczema, atopic dermatitis is the most common and often also presents alongside hay fever or asthma – but not always [1].

The common assumption that eczema is ‘just’ a skin condition that affects children is untrue. It is believed that 10% of children experience eczema, and while this can often drop in the teen years (for reasons not yet known), adult eczema remains persistent. Depending on the study, 10–50% of adults report onset of eczema during adulthood [2], and it has been estimated that a total of 15 million people in the UK alone experience the condition [3].

What causes eczema?

The primary cause of eczema is believed to be associated with the skin barrier. The skin barrier plays a crucial role in our health. It protects the body against external pathogens and diseases and is also critical for maintaining healthy skin as it helps to lock in moisture [4].

Transepidermal water loss (or TEWL) is a key component to the presence and management of eczema. It is often associated with a deficiency of filaggrin, a protein component of the epidermis. As well as helping the aggregation of filaments that help maintain the structural integrity of the upper epidermis (the outer layer of the skin), filaggrin helps maintain hydration and pH. Lower or no filaggrin in the skin therefore leads to loss of barrier function, reduced levels of the skin’s natural moisturizing factors and an increase in pH. This trio creates the perfect conditions for the onset of eczema [4].

But, unfortunately, the development of eczema is not quite that simple… Further research has shown that the balance and diversity of bacteria on the skin (the skin microbiome) also has a role to play.

What role does the skin microbiome have?

There has been an explosion of research to investigate the role of the skin microbiome in our health. The hope is that with a better understanding, it can be used to help treat skin conditions or promote skin health.

So, what do we know about eczema and the skin microbiome? Research has shown that changes in the skin microbiome influence the development and degree of symptoms.

Chronic inflammation of the skin, as is present in eczema, causes skin barrier impairment. The skin microbiome also influences the barrier by mediating the effects of various factors, including temperature and humidity. When the barrier is disrupted, this can subsequently further the impacts of TEWL – leading to an infuriating cycle for those with eczema. As such, skin hydration is essential in controlling eczema [1,4].

Many studies have shown that individuals with eczema have a higher incidence and proportion of Staphylococcus aureus bacteria in their skin microbiome than healthy individuals. In fact, 7/10 of those affected by atopic dermatitis carry S. aureus on the skin, compared to 1/5 of healthy individuals. This provides a potential target for intervention. Proportional differences in other microbes have also been linked to atopic dermatitis. Frustratingly, the loss of skin barrier function as described above provides the optimal growth conditions for S. aureus [4].

For those with eczema, the interlinked nature of skin barrier impairment and the balance of the skin microbiome is a significant step forward in understanding why eczema develops.

Using the microbiome to alleviate eczema

An array of emerging treatments and technologies are being designed to target and manipulate the microbiome to treat chronic skin complaints. However, in the meantime, there is hope a little closer to home that may offer a relief for those with eczema.

As well as the skin itself, we know that the gut has an interesting – and potentially crucial – role in the development of the condition. Imbalances in our gut microbiome (gut dysbiosis) allow certain bacteria to thrive while others decline. These changes can also impact our immune system balance, with both skin and gut microbiome dysbiosis now linked to altered immune responses and the development of various skin diseases. When it comes to eczema, those affected have been repeatedly shown to have different gut bacterial communities to healthy individuals e.g. Escherichia coli and S. aureus are increased and Bacteroides species decreased [4].

Combined with various and diverse environmental factors (stress, diet, pollutants), the gut’s microbial dynamics can therefore contribute to the development of eczema.

While more work is needed to understand the mechanisms by which the gut microbiome affects the immune responses in the skin (and vice versa), emerging evidence has subsequently indicated that restoring a healthy gut microbiota may be a therapeutic target [5].

For now, holistic health and wellbeing, and use of available products such as probiotics, may be a good place for individuals to start in their day-to-day management of eczema. Those affected should also consult a doctor or dermatologist in order to create a safe and effective management plan.






5. Lee, S.-Y. Allergy Asthma Immunol Res. 10, 354–362 (2018).

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