I was recently looking at the calluses on my hands after a period of intensive gym training and found myself reflecting on just how remarkable the human body really is.
A callus, or hard skin, develops because the body recognises repeated friction or pressure and responds by making the skin thicker and stronger. When minor trauma occurs, the body adapts to make future trauma less impactful. It’s an intelligent protective response.
At Mosaic Medical, we often see this same principle playing out throughout the body. Many chronic health conditions can be understood as the body’s attempt to protect us. The challenge is that sometimes these protective mechanisms become overactive or continue long after the original threat has disappeared.
The Body’s Protective Response to Trauma
When a significant emotional or psychological trauma occurs, the body can develop protective strategies designed to keep you safe.
For example, someone who has experienced a traumatic event may notice a rapid heart rate, anxiety, or a strong emotional reaction when returning to a place associated with that experience. These responses are not signs that the body is malfunctioning. Rather, they are evidence that the nervous system is attempting to prevent future harm.
One fascinating example involves sleep.
Sleep is far more than a period of rest. During rapid eye movement (REM) sleep, the brain helps process emotional experiences and consolidate memories. Researchers have proposed that REM sleep plays a particularly important role in “extinction learning” – the process through which the brain learns that something which was once dangerous is no longer a threat.¹
People living with post-traumatic stress disorder (PTSD) commonly experience disturbances in REM sleep. Researchers believe these changes may impair emotional memory processing and fear extinction, potentially contributing to the persistence of symptoms such as hypervigilance, anxiety, sleep disturbance, and strong reactions to seemingly minor triggers.² ³
From a functional medicine perspective, this can be viewed as the body trying to protect you from reliving a traumatic experience. However, when this protective mechanism remains switched on, it may prevent the original event from being fully processed, allowing symptoms to persist for years.
Autoimmunity: When Protection Becomes Misdirected
The immune system exists to keep us safe.
Every day it identifies and responds to viruses, bacteria, toxins, and other potentially harmful substances. To do this, it produces antibodies that recognise and target foreign invaders.
Occasionally, however, the immune system can become confused.
One of the most widely studied theories in autoimmunity is known as molecular mimicry. This occurs when the immune system creates antibodies against a foreign substance, such as a virus, bacterium, or food-derived protein, and those antibodies also recognise similar-looking proteins within the body’s own tissues.⁴
In effect, the immune system is doing exactly what it was designed to do – protecting us from perceived threats. The problem arises when it can no longer reliably distinguish between a foreign invader and part of the body itself.
A commonly discussed example is Hashimoto’s thyroiditis, an autoimmune thyroid condition. Researchers have explored whether proteins found in certain foods, including gluten, may share structural similarities with thyroid tissue in susceptible individuals. While the relationship is complex and remains an active area of research, molecular mimicry and immune cross-reactivity provide biologically plausible explanations for why environmental triggers may contribute to autoimmune processes in some people.⁴
Again, this is not a body attacking itself for no reason. It is a protective system that has become overly vigilant.
Histamine, Mast Cells and the Nervous System
We see a similar pattern in people struggling with histamine-related symptoms.
Histamine is a crucial chemical messenger involved in immune function, inflammation, and protection against potential threats. It is released from specialised immune cells called mast cells whenever the body perceives danger.
This response is incredibly useful when dealing with genuine threats such as infections, allergens, or injury.
However, mast cells do not only respond to physical threats. Research has demonstrated extensive communication between the nervous system and mast cells, meaning that psychological stress, emotional distress, and nervous system activation can directly influence histamine release.⁵
In some individuals, the mast cell system appears to become excessively sensitive. Foods, environmental exposures, hormonal changes, poor sleep, emotional stress, or even seemingly minor nervous system triggers can provoke histamine release.
The symptoms can be wide-ranging and include:
- Flushing
- Itching
- Headaches
- Digestive symptoms
- Nasal congestion
- Anxiety
- Heart palpitations
- Fatigue
From this perspective, histamine-related symptoms may represent a body that has become highly sensitised to danger signals, even when no genuine threat is present.
Once again, the body is trying to protect you. The issue is not a lack of protection, but protection that has become excessive.
Why Feeling Safe Matters for Health
Whether we’re talking about PTSD, autoimmune conditions, histamine intolerance, mast cell activation, or other forms of chronic illness, a common theme often emerges.
The body has become stuck in a protective mode.
The nervous system, immune system, or inflammatory pathways continue responding as though a threat is present, even when it is no longer there.
This understanding can change the way we think about healing.
Instead of asking, “Why is my body attacking me?” a more helpful question may be, “What is my body trying to protect me from?”
At Mosaic Medical, much of our work involves helping patients identify the factors that may be keeping their body in this heightened protective state. This may involve addressing nervous system dysregulation, supporting gut health, investigating immune triggers, improving sleep, correcting nutritional deficiencies, or exploring unresolved stress and trauma.
The goal is not simply to suppress symptoms. The goal is to help the body recognise that it is safe.
The Lesson from a Callus
If I stopped doing intensive gym training tomorrow, the calluses on my hands would gradually soften. Without repeated stress, the body would no longer need that extra layer of protection.
Many chronic symptoms can be viewed through a similar lens.
The body developed protective adaptations for a reason. Those adaptations may once have been useful. But if the original threat has passed, they can become barriers to long-term health and wellbeing.
Healing often involves helping the body let go of protections that are no longer needed.
The remarkable thing is that the same intelligence that created those protective responses also has the capacity to reverse them.
Sometimes, the first step is simply helping the body remember that it is safe again.
Dr Andie Siggers
References
- Pace-Schott EF, Germain A, Milad MR. Sleep and REM sleep disturbance in the pathophysiology of PTSD: the role of extinction memory. Biology of Mood & Anxiety Disorders. 2015;5:3.
- Murkar A, De Koninck J. Consolidative mechanisms of emotional processing in REM sleep and PTSD. Sleep Medicine Reviews. 2018;41:173-184.
- Ogden J, Jobson L, Drummond SPA. Does Sleep Reduce Intrusive Memories After Analogue Trauma? Current Sleep Medicine Reports. 2024;10:1-12.
- Krysiak R, Szkróbka W, Okopień B. Beyond celiac disease: the potential role of gluten in Hashimoto’s thyroiditis. Frontiers in Endocrinology. 2026.
- Xu H, Shi X, Li X, Zou J, Zhou C, Liu W. Neurotransmitter and neuropeptide regulation of mast cell function: a systematic review. Journal of Neuroinflammation. 2020;17:356.