Stressed woman at computer pinching the bridge of her nose in frustration

How stress throws the immune system out of balance

Have you ever felt stressed and overwhelmed due to an intense work deadline and then come down with an illness, which couldn’t come at a worse possible time? Or had several busy and stressful months, only to get sick once you finally get a break? This is no coincidence. The immune system is directly disrupted by the body’s response to stress with prolonged stress putting you at greater risk of infection and increasing the time it takes to recover.


How does stress affect the immune system?

Not all stress has a negative effect on immunity. Studies show that short term stress, like a job interview or public speaking, can actually boost some parts of the immune system.1 However, when stress becomes chronic, our immune defences can become compromised.1

The stress response (aka. ‘fight or flight’) involves a well-orchestrated cascade of events in which stress hormones like adrenaline and cortisol are released. They provide your body with a burst of energy, increase your heart rate, elevate your blood pressure, send glucose and oxygen to the brain and sharpen your senses so you can ‘fight or flee’ from what it perceives as a threat or danger. The stress response is the same whether you’re faced with a life-threatening event like an oncoming car or something non-life threatening like day-to-day family problems. These stress hormones also curb the functions that it considers non-essential for a fight or flight situation. They alter the body’s immune responses and reduce digestive activity.2 The body’s stress response is usually self-limiting and once the stressor or threat passes, hormone levels return to normal, and the body’s systems resume their regular functions. However, many people are unable to regulate stress. Chronic low-level stress keeps the body revved up and on high alert. The constant release of cortisol and adrenaline can wear the body down physically and mentally and put you at risk of many health problems. Research shows that long-term activation of the stress response fatigues and suppresses the parts of the immune system that defend against many types of infections.1 It has also been shown to increase inflammation and diminish the immune system’s ability to produce antibodies in response to vaccination.1


How do you know if you’re stressed?

Stress that’s left unchecked can affect our body and emotions in lots of different ways. Common signs to look out for include:3


  • Feeling overwhelmed or unable to cope
  • Feeling ‘on edge’ or irritable
  • Sleeping difficulties
  • Changes in appetite
  • Inability to focus or concentrate
  • Frequent headaches
  • Muscle tension
  • Digestive problems or exacerbation of digestive issues
  • Changes in mood or increased anger
  • Withdrawal from friends or family
  • Regular mild upper respiratory tract infections like the common cold4


If you experience more than one of these signs and symptoms, it might be time to take steps to help manage your stress in healthy ways.


Things you can do to help your body recover from stress and support your immune system

There are many different techniques you can use to help counter chronic stress, which will in turn benefit your immune system.


  • Get physically active.

    Exercise can reduce the build-up of stress by improving breathing and reducing muscle tension. It also helps to strengthen the body’s immune responses. Find an activity that you enjoy so it can become a sustainable habit like brisk walking, jogging, hiking, bike riding, tennis, Pilates, surfing, swimming, etc.

  • Incorporate relaxation practices

    into your daily routine such as yoga, meditation, tai chi, Qi gong or general mindfulness activities. These encourage you to relax, slow your breath and focus on the present to induce calm.

  • Try a calming breathing technique

    When we’re stressed, our breathing tends to be shallow and from our upper chest. When we consciously breathe deeper into our abdomen, it can encourage the body to relax and dampen the stress response. An easy technique to remember is box breathing - Inhale for a count of 4, hold the breath for a count of 4, breathe out for a count of 4 and hold the breath out for a final count of 4. Repeat 4 times.

  • Maintain social support

    Maintaining social connections can make you more resilient to stressful events, improves your mental wellbeing and provides comfort when stress becomes overwhelming. Book regular catch ups with friends and family, join a club or engage in a hobby where you can meet people who share your passions, call or send texts to your favourite people to let them know you appreciate them or volunteer in your community. Reach out to your support circle when you’re feeling overwhelmed. As the old adage goes, “a problem shared, is a problem halved”.


How probiotics can help

The gut and brain are closely connected and recent advances in research have described the importance of the gut microbiome in this relationship. The probiotic strain Lactobacillus plantarum 299v has been shown to reduce levels of the stress hormone, cortisol.5 Probiotics have also been found to buffer against the detrimental effects stress can have on memory, learning and other cognitive functions.6 While helping reduce stress with probiotics can indirectly help minimise the negative impact on the immune system, probiotics also have direct effects on immune health. A large proportion of the body’s immune system resides in the gut and relies on the gut microbiome. The microbiome protects the body from invading pathogens, helps balance inflammatory responses and strengthens the gut wall, which plays an important role in protecting the body from harmful substances.7 Taking a high quality probiotic supplement, with bacteria strains that are backed by science, may help your body fight the effects of stress and support your immune resilience.


  1. Segerstrom S et al, 2004, ‘Psychological stress and the human immune system: a meta-analytic study of 30 years of inquiry’, Psychological bulletin,vol 130, no 4
  2. Chu B et al 2021, Physiology, Stress Reaction. StatPearls Publishing, accessed 6 September 2022,
  3. Health Direct, 2021, Stress, Accessed 5 June 2023,
  4. Seiler, A et al, 2020, ‘The Impact of Everyday Stressors on the Immune System and Health’, In: Choukèr A. (eds) Stress Challenges and Immunity in Space. Springer, Cham
  5. Andersson H et al, 2016, ‘Oral Administration of Lactobacillus plantarum 299v Reduces Cortisol Levels in Human Saliva during Examination Induced Stress: A Randomized, Double-Blind Controlled Trial.’ Int J Microbiol, vol 2, pp 1
  6. Papalini S et al 2019, ‘Stress matters: Randomized controlled trial on the effect of probiotics on neurocognition’, Neurobiology of stress, vol 10
  7. Takiishi T et al, 2017, ‘Intestinal barrier and gut microbiota: Shaping our immune responses throughout life’, Tissue barriers, vol 5, no 4
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