Can an unhealthy gut contribute to skin problems such as acne or eczema?
A disrupted gut microbiome is associated with acne and eczema, although that association has not yet been proven to be cause and effect. Eating more fibre and plant-based foods is a sensible first step; for targeted probiotics the evidence is still too mixed for a clear recommendation.
Acne and eczema are not purely a skin matter. Multiple review studies describe a so-called 'gut-skin axis': the microbiome in your gut influences your immune system and the skin barrier, and that effect can trigger or worsen skin diseases. People with acne or eczema turn out to have a disrupted gut microbiome more often than people without these complaints. This is a consistent pattern in the literature, although it largely concerns associations rather than proven cause and effect.
In eczema, the association has been described most extensively. A disrupted gut microbiome appears to weaken the skin barrier and make the immune system more susceptible to inflammatory responses. In acne, the skin microbiome itself also plays a role alongside gut bacteria: less diversity on the skin goes hand in hand with more symptoms. Exactly how the gut and skin communicate with each other has not yet been fully unravelled.
Diet appears to be a relevant point of intervention. A diet rich in fibre, antioxidants and plant-based compounds seems to reduce skin inflammation, presumably because it has a beneficial effect on the gut microbiome. The evidence for this is still limited and not strong enough for firm recommendations, but it is biologically plausible.
Probiotics, synbiotics and postbiotics are attracting a great deal of attention as possible additions in the treatment of acne and eczema. Results are mixed: in some people and conditions studies do show improvement, but there is no consistent evidence that this works for everyone. Which specific bacterial strains are most beneficial remains unclear.
A practical consideration in acne treatment: antibiotics, both applied to the skin and taken orally, can in turn disrupt the microbiome on the skin. That risk is increasingly being factored in when looking for alternatives.
All claims are based on review and overview literature (multiple PMIDs). The evidence is predominantly associational; large interventional RCTs in humans are still largely lacking.