The Gut-Brain Axis
What If Your Mood, Migraines and Skin Are Connected?
You feel anxious without understanding why. Your mood changes, You struggle to concentrate, migraines return, your skin reacts, or your hair begins to fall more than usual.
These symptoms may appear unrelated and affect completely different parts of the body. Yet they may sometimes share part of the same biological story.
That story may begin in the gut.
More Than a Digestive Organ
The intestine does much more than digest food. It communicates continuously with the brain, immune system and the rest of the body.
This communication is called the gut–brain axis. It operates through several pathways:
the vagus nerve, connecting the gut and brain;
the enteric nervous system, formed by more than 100 million neurons inside the digestive tract;
hormones and immune signals;
substances produced by gut bacteria;
the bloodstream.
The connection works in both directions. Stress can change digestion and intestinal movement. At the same time, inflammation or microbial changes in the gut can influence brain function.
This is why emotional stress can cause nausea, diarrhoea or constipation, and why intestinal disruption may sometimes appear through changes in mood, concentration or behaviour.
When the Gut Ecosystem Changes
The intestine is home to trillions of microorganisms, collectively known as the gut microbiome.
These microbes interact with food and produce substances involved in immune regulation, intestinal barrier function and communication with the nervous system.
Diet, stress, sleep, infections, medications and environmental exposures can all change this microbial environment.
When the balance or activity of the microbiome becomes disturbed, it is known as dysbiosis. In some people, dysbiosis may reduce the production of beneficial microbial substances, weaken intestinal barrier function and increase inflammatory activity.
If the intestinal barrier becomes more permeable, microbial components and inflammatory signals can enter the circulation more easily. From there, they may influence other tissues, including the brain and skin.
The effect is not necessarily a stomach ache. It may appear somewhere else entirely.
Your Mood May Not Begin Only in Your Mind
Approximately 90–95% of the body’s serotonin is produced in the intestine. However, intestinal serotonin does not travel directly into the brain.
Instead, the gut influences mood through the vagus nerve, immune activity and the metabolism of tryptophan, the amino acid used to produce serotonin.
In 2025, Harvard Medical School researchers identified a more specific connection involving the bacterium Morganella morganii, previously associated with major depressive disorder.
They found that this bacterium could interact with an environmental micropollutant to produce unusual molecules. These molecules activated the immune system and increased interleukin-6, an inflammatory signal also associated with depression.
The study did not suggest that one bacterium explains every case of depression. It demonstrated something more important: a measurable pathway through which a gut microbe, an environmental exposure and inflammation may become biologically connected to mood. Read the study.
Research also suggests that microbial signals may interact with brain pathways involved in anxiety, emotional processing, motivation and behaviour.
The brain remains central, but it does not operate separately from the body.
Could Migraine Begin In The Gut ?
This pattern is part of the foundation of Wholiera. More than a decade ago, the founder began observing a recurring link between severe migraines and digestive symptoms through her personal health experience.
Many people with migraine also experience bloating, nausea, constipation, diarrhoea or food-related digestive discomfort.
A 2025 systematic review found differences between the gut microbiota of people with migraine and healthy controls. These included lower microbial diversity, reduced levels of bacteria associated with anti-inflammatory activity, and increased levels of other bacteria.
This does not mean that every migraine originates in the gut. Migraine is multifactorial and may involve several underlying factors, including genetics, hormonal fluctuations, disrupted sleep, stress, nervous-system sensitivity, neurovascular changes and environmental or dietary triggers.
But when migraines and digestive symptoms repeatedly occur together, gut inflammation and the gut microbiome may be part of the same physiological picture, rather than two unrelated problems
Brain Fog Is Also a Physical Symptom
Difficulty concentrating, slowed thinking, memory problems and mental fatigue are commonly described as “brain fog.”
Inflammatory signals produced outside the brain can affect communication between the immune and nervous systems. Changes in microbial metabolites may also influence energy regulation and the biological compounds used by the brain.
The gut may therefore contribute to brain fog in some people, particularly when it appears alongside digestive disturbance or chronic inflammation.
Other causes, including iron deficiency, thyroid dysfunction, poor sleep and prolonged stress, must also be considered. The symptom is real, but its origin may involve several systems at once.
What If the First Visible Sign Appears on Your Skin?
The skin may be showing what the gut keeps hidden.
Researchers have found differences in the gut microbiome of people with acne, eczema, psoriasis and rosacea. The gut may influence the skin through inflammation, the immune system, substances produced by gut bacteria and changes in the protective barriers of both the intestine and skin. Recent studies continue to support this connection, particularly in conditions such as atopic dermatitisand psoriasis.
A breakout does not prove that the gut is imbalanced. But recurrent skin inflammation may not always be a surface-only problem.
The same broader picture may apply to hair loss. The digestive system absorbs nutrients that supports normal hair growth, including iron, zinc, vitamin B12, folate, protein and essential fatty acids.
Digestive imbalances may affect how effectively the body absorbs and uses these nutrients. Researchers are also investigating the gut microbiome’s possible role in inflammatory and autoimmune forms of hair loss. Some studies suggest that the gut microbiome may influence how the body regulates and processes androgen hormones, including DHT, a hormone involved in certain types of hair loss.
Hair loss remains multifactorial, but when it appears with digestive symptoms, nutrient deficiencies or inflammation, the gut may be part of the wider biological picture.
The Functional Health Approach
Supporting the gut–brain axis is not about choosing one trendy supplement or assuming that every sign is caused by dysbiosis.
It begins by looking for patterns:
Did the digestive symptoms begin before the migraines or skin changes?
Are anxiety or mood changes stronger during periods of intestinal discomfort?
Is hair loss accompanied by low iron, poor digestion or dietary restriction?
Have antibiotics, medications, infection or prolonged stress changed bowel habits?
Does the diet provide enough fibre and protein, with sufficient dietary diversity?
The next step is to consider the intestinal environment as a whole: digestive function, food quality, the gut microbiome, nutrient status, inflammation, sleep and stress physiology.
The objective is not to view the symptom as an isolated sign, but to understand the cause behind it.
Your mood, migraines, skin and hair do not always prove that something is wrong in your gut. But they should not always be viewed as completely separate problems.
Sometimes, the visible symptom is only one part of a much larger biological connection.
Wholiera’s interest in the gut–brain connection began more than a decade ago through its founder’s personal health experience. [Discover the story behind Wholiera.]
