Post viral infection mood changes in children, a chance to dig deeper into possible root causes.
This blog is for the parents who notice changes in their child’s mood, behaviour, sleep, anxiety, or emotional resilience following ongoing bacterial or viral illnesses. These changes can seem sudden or out of character, especially after repeated infections, poor gut health, or periods of chronic stress on the body. In some children, these patterns may overlap with immune and nervous system response, and may be considered as part of the PANS - Paediatric Acute-onset Neuropsychiatric Syndrome.
As a Clinical Nutritionist, I often see families searching for answers after being told that everything appears “normal,” despite clear changes in their child’s wellbeing. This is where functional testing may help provide a deeper understanding of what could be contributing to symptoms.
The Gut-Brain Connection and Children’s Health.
The gut and brain communicate closely through what is often referred to as the gut-brain axis. When gut health is disrupted, it may influence mood, emotional regulation, concentration, sleep, immune function, and behaviour.
A microbiome stool analysis can help assess areas such as:
Digestive function
Gut inflammation
Beneficial bacteria diversity
Bacterial or fungal overgrowth
Gut permeability markers
Immune activity within the digestive tract
For some children, ongoing gut inflammation or microbial imbalance may place additional stress on the nervous and immune systems.
How Nutrigenomic Testing May Help.
Nutrigenomic testing looks at how genetic patterns may influence areas including:
Inflammation pathways
Stress resilience
Histamine balance
Neurotransmitter function
Detoxification pathways
Vitamin and nutrient metabolism
Methylation support
Rather than using a one-size-fits-all approach, Nutrigenomic analysis can help guide more personalised nutrition, lifestyle, and supplement strategies based on the individual child.
A Functional Testing Case Example:
With permission from both the patient and his family, I can briefly share a case example involving a young boy who experienced a sudden and significant shift in mood and behaviour following a difficult year of illness.
Although there was never a formal diagnosis of PANS, the family described the behavioural changes as aggressive, emotionally reactive, and very unlike his normal personality. Symptoms appeared after a year involving recurrent viral and bacterial infections, including tonsillitis and strep throat requiring tonsil removal surgery.
As we worked through his health timeline, several important pieces emerged:
A history of significant mould exposure during home renovations
Recurrent infections (including strep throat) quite intensely, within a 12 month period
A severe stomach bug while overseas
Increasing food fussiness
Poor bowel habits, sometimes going up to a week without a bowel motion
Reduced resilience at school, sport, and socially
Initially, my clinical support was largely trial-and-error. While some interventions helped temporarily, symptoms would often return. Once functional testing was introduced more intentionally, clearer patterns began to emerge.
What Testing Revealed:
Standard pathology testing identified:
Low Vitamin D
Low Zinc
Low B12
Elevated folate
Coeliac negative, but with elevated IgA marker
MMM stool analysis showed:
Bacterial overgrowth contributing to intestinal toxicity
Elevated inflammatory markers
Fungal overgrowth
Low beneficial bacterial diversity
Nutrigenomic analysis identified patterns relating to:
Methylation pathways
Fatty acid metabolism
Neurotransmitter support
Vitamin D, A, and C metabolism
Pro-inflammatory tendencies
Using this information, a more targeted support plan was developed, including:
Vitamins, minerals, and amino acids tailored to his Nutrigenomic profile
HMO fibre to support beneficial gut bacteria and regular bowel motions
IgG support for intestinal integrity and inflammation
Targeted probiotics
Omega-3 fatty acids and Vitamin C
Over the next 4 months, the family noticed significant improvements in mood, resilience, digestive function, and overall wellbeing.
Looking Deeper - When Symptoms Don’t Add Up.
Every child is different, and there is rarely one single cause behind complex symptoms. Functional testing is not designed to diagnose conditions such as PANS, but it may help uncover hidden stressors that could be contributing to inflammation, digestive dysfunction, immune imbalance, or nervous system stress.
Additional testing to consider may include:
Micronutrient testing
Mould exposure assessment
Heavy metal testing
Standard pathology investigations
If your child has experienced ongoing mood, behavioural, digestive, or immune-related changes following illness, and you feel there may be missing pieces to the puzzle, functional testing may help provide more personalised insights and direction.
To learn more about functional testing, Nutrigenomics, or MMM stool analysis, or to discuss whether this approach may be suitable for your child, make sure to reach out!