The link between eczema, gut health, and the microbiome

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Yes — research suggests that eczema and gut health are linked.

The body contains many species of microorganisms, including bacteria, fungi, and viruses. These organisms have different effects on human health.

Most of these microbes live inside the gut, particularly the large intestine. However, some also live on the skin. Scientists have discovered that the gut microbiome and skin microbiome influence each other.

When there is an imbalance in the gut or skin flora, it is known as dysbiosis. This can happen if there:

• are too many “bad” species
• are not enough “good” species
• is not enough diversity of species

In people with atopic dermatitis, which is a type of eczema, dysbiosis may play a role in the development of the disease.

Here is what researchers know so far about the connection.

Dysbiosis

Studies have shown that, in people with atopic dermatitis, there is often a compromise to the health of their gut microbiome. The 2021 review notes that atopic dermatitis is associated with:

• lower bacterial diversity
• lower levels of beneficial species, such as Bacteroidetes, Akkermansia, and Bifidobacterium
• higher amounts of harmful bacteria species Staphylococcus aureus

Specifically, people with atopic dermatitis can have higher levels of

• Staphylococcus aureus
• Faecalibacterium prausnitzii
• Clostridium
• Escherichia

They may also have lower levels of helpful species of bacteria, such as:

• Bacteroidetes
• Akkermansia
• Bifidobacterium

This points to a connection between dysbiosis and atopic dermatitis.

Immune response

Atopic dermatitis symptoms occur due to the immune system. When the immune system perceives a threat on the skin, it creates inflammation in response. This is what causes the itchy rash.

Scientists believe that dysbiosis in the gut and on the skin may cause this. It may be that the immune system is detecting harmful levels of “bad” microbes on the skin and so reacts to them. Dysbiosis and eczema may then create a cycle of inflammation that perpetuates symptoms.

According to the 2021 review, changes in the microbiome may also alter the immune response, causing it to dysregulate.

Intestinal permeability

The walls of the intestines are permeable. This means substances can pass through them. In some people, the intestinal walls allow more to pass through than they should. Some refer to this as “leaky gut,” although this is not a standalone medical diagnosis.

Scientists know that some beneficial species of bacteria produce byproducts that help the intestinal barrier work more effectively. These include some of the species people with atopic dermatitis can have less of, such as Bifidobacteria.

This may explain why some studies have found a correlation between atopic eczema and an increase in intestinal permeability. However, more research on this is necessary to fully understand the connection.

Many aspects of daily life influence the microbiome. Dysbiosis may develop due to:

• Oral antibiotics: Oral antibiotics work by killing all species of bacteria they come into contact with. This means they do not discriminate between “good” and “bad” species that live in the gut. Repeated or long-term courses of antibiotics are associated with dysbiosis.
• Other medications: A 2020 study evaluated the effect of different medications on the microbiome and found that those with the strongest link to dysbiosis – aside from antibiotics – included laxatives, metformin, and proton pump inhibitors (PPIs).
• Smoking and nicotine: A 2021 review states that in previous research, people who smoked had higher amounts of harmful bacterial strains and lower amounts of beneficial strains. Researchers also found quitting smoking resulted in increased diversity.
• Lack of human contact during and after birth: A vaginal birth, skin-to-skin contact, and breastfeeding all give newborn babies early exposure to another human’s microbiome, allowing them to start developing their own. However, babies who arrive via Cesarean section, have little contact with others, or who only receive formula may miss out on this. This disproportionately affects people from low-income backgrounds.

Many other things also have an impact on the microbiome, although there is less research connecting them directly to dysbiosis. They include:

• Diet: The Western diet tends to be high in inflammatory foods, such as saturated fat, which may contribute to dysbiosis.
• Lack of vitamin D: Sunlight contains UVB rays, which allow the skin to make vitamin D. Vitamin D is associated with more diversity in the microbiome, so a lack of this nutrient may inhibit diversity.
• Stress: A 2018 study states that animal research indicates stress adversely affects the microbiome. More research is necessary to prove the effect on humans.

Some scientists believe that the modern preference for washing and bathing regularly and using cleaning products around the home may be damaging the microbiome. This may explain why rural and Indigenous communities tend to have lower rates of inflammatory diseases than urban ones.

However, the “hygiene hypothesis” is currently only a theory. There could be other aspects of urban lifestyles that explain the difference.

There is currently no way to test if someone’s eczema is gut-related. However, there are some diagnostic tests a doctor could use to assess someone’s overall gut health. They include:

• a gut microbiome test
• an intestinal permeability test
• a Calprotectin test, which measures gut inflammation

It is worth noting that, because there are so many species in the microbiome, microbiome tests cannot measure every species.

Learn more about microbiome testing here.

The microbiome is very responsive to changes in diet. Through food, a person may be able to promote more “good” bacteria.

A 2021 study examined the effect of different foods on the composition of the gut microbiome. The authors found that a certain diet links to higher amounts of microbial species that have anti-inflammatory effects. The eating plan the researchers tested had more focus on plant-based foods and less on animal-based foods.

Foods to eat included:

• fruits
• vegetables
• beans and peas
• nuts
• low-fat fermented dairy foods, such as yogurt
• fish

Foods to avoid included:

• alcoholic drinks
• sodas
• high-fat processed meats

However, it is important to note that this is not a cure for eczema. Instead, dietary changes may support overall health. This can have a knock-on effect on the skin and reduce symptoms for some people.

The Department of Veterans Affairs recommends following an anti-inflammatory diet to reduce eczema symptoms.

Learn more about eczema and diet here.

Probiotics are another name for “good” microorganisms that are part of the microbiome. People can get them from food or supplements. The research so far on whether probiotics help with eczema is mixed.

The 2021 review notes that a number of studies have shown Lactobacillus and Bifidobacterium to be helpful for atopic dermatitis. They may also have a protective effect on the microbiome when a person has to take antibiotics, which may reduce the risk of developing dysbiosis.

However, a 2018 review of 39 clinical trials with 2,599 participants found that the supplements made little or no difference in relieving eczema symptoms, such as sleep loss and itchiness.

This suggests probiotics may not be a treatment for eczema but may help promote gut health or prevent imbalances.

It is worth noting that probiotics are not always suitable for everyone and that they can have side effects and risks. Speak with a doctor before trying any new supplement or major dietary change.

Learn more about probiotics and their potential side effects here.

If someone suspects that their eczema may be related to dysbiosis, they can speak with a doctor to get more information on the options available to them.

A person may want to ask the following:

• Could I have dysbiosis?
• Is there a way to test for it?
• What could have caused it?
• Could my medication be damaging the microbiome? If so, what other options are there?
• What can I do to help my skin and gut microbiome?
• Can I try an anti-inflammatory diet? If so, how should I start?
• Can I try a probiotic supplement? Do you have recommendations?

The link between eczema and gut health lies in the gut-skin axis, which refers to the way intestinal flora influence the microbes that live on the skin. Scientists are not sure how this works but believe that an imbalanced microbiome may play a role in the inflammation and immune response that causes eczema.

Microbiome imbalance, or dysbiosis, is when someone has too many “bad” species of microbe, not enough “good” species, or a general lack of diversity.

Making changes that promote a healthy microbiome, such as eating a plant-based and anti-inflammatory diet, may help some people with their symptoms. However, more research is necessary to understand how the microbiome may be relevant to eczema treatment.