Whether you're avoiding that chesty cough doing the rounds at the office, sporting a burn on your finger from last night's cooking mishap, or you've rubbed your eye straight after holding onto the handrail on the shopping mall escalator, our immune system is always hard at work.
It protects us from the billions of bacteria we share our lives with, goes into battle when a virus comes our way, and works around the clock to safeguard our health so our body can function at its best.
Our incredible ability to heal and fight infection has helped to ensure our species' survival throughout the ages, and no machine or synthetic medicine has yet been able to replicate the power of our natural immunity.
But just as the body can put up a fight when our health is at risk, it can also wage war against itself. There are thought to be around 100 different autoimmune illnesses in existence, but each shares a common link – they all arise from the body's immune system mistakenly attacking its own healthy cells.
Conditions such as lupus, rheumatoid arthritis, type 1 diabetes, coeliac disease, inflammatory bowel disease and multiple sclerosis fall into the autoimmune disorder category, and while the symptoms can be managed, there is no known cure.
Across the world, rates of autoimmune illnesses are thought to have risen up to seven per cent a year for the past three decades – and it's a worrying trend that's left experts scratching their heads.
Genetics can be a factor – some types of autoimmune diseases run in families – but new research into epigenetics has focused more on the ways in which certain genes can get 'switched on and off' due to environmental factors.
Theories to explain the triggers for this mysterious group of illnesses have led medical experts to look at everything from environmental toxins; low levels of vitamin D; the hygiene hypothesis (living in increasingly sterile environments); and certain types of infections to close in on a possible cause.
Meanwhile, others in the health field are focused on the way in which lifestyle factors like diet and stress levels can aggravate or improve the symptoms of autoimmune illnesses.
The inflammatory factor
While symptoms can vary hugely from person to person, autoimmune diseases share one common feature – higher levels of inflammation in the body.
It might not be possible to reverse or cure an autoimmune illness, but there's growing evidence that eating a diet rich in immunity-boosting, anti-inflammatory foods can help.
"Management is the key word when it comes to autoimmune conditions," says registered clinical nutritionist Natalie Brady. "From a dietary perspective, this is all about reducing inflammation as much as possible."
Natalie says a back-to-basics approach, like choosing natural wholefoods and focusing on colourful fruits and veges, is a good place to start and following a gluten-free diet can be a key piece of the puzzle for many autoimmune sufferers.
"Gluten is the biggest thing to avoid, for any inflammatory condition," Natalie explains.
"The main issue with gluten is that it increases gut permeability, which can make us more prone to a condition called 'leaky gut'. There's a lot of research around about the link between gut health and autoimmune conditions, so anything to support gut health can be a massive benefit to autoimmune sufferers."
Dairy, processed sugar, refined carbs and alcohol can also have an inflammatory effect for some, although how far you have to go to reduce these in the diet depends on the individual, and is up for debate among professionals.
"My personal approach would be to remove gluten and processed sugar completely, because of that gut permeability factor, and limit dairy in the initial stages," says Natalie.
"It's often best for people to think, 'Right, let's have a big diet and lifestyle overhaul' because you really want to get in there and reduce anything that might cause an inflammatory reaction. Opinions vary a lot, but I think that if we're having just a little bit of gluten every other day, it's not giving the body a chance to heal.
"I always recommend a wholefood diet for at least six to eight weeks, preferably 12 weeks, then assessing it after that. It depends a lot on the person and the specific type of autoimmune illness, but it often takes 12 months to see a big difference, longer if the symptoms are really severe. It can really come down to the individual person and their motives to change their diet."
Some triggers make autoimmune diseases worse
Due to the many types of autoimmune illnesses, the wide range of potential triggers and huge variations in disease progression and symptoms, getting a definitive diagnosis can be difficult.
"It's such a massive topic, there's lots of research to suggest things that can help, but it's still such an unknown field," Natalie explains. "The research around it is immense, just staying on top of all of that is difficult in itself."
While the statistics for this corner of the world are unclear, the American Autoimmune Related Diseases Association says up to 50 million people in the US are affected, with an average five-year wait to receive a diagnosis.
On our shores, Natalie says thyroid-related issues are among the most common autoimmune complaints she sees at her clinic. "It's across the board, from overactive thyroid conditions like Graves' disease, to Hashimoto's thyroiditis, which is an underactive thyroid, and it's all related to when antibodies produced by the immune system attack the thyroid gland," she explains.
"I haven't seen any official numbers but I do think there are a lot of people out there with immune dysregulation issues. Other conditions I see often are chronic fatigue syndrome and rheumatoid arthritis. For some people, it may be chronic low-grade inflammation, and it can be years before they develop specific symptoms. It may be a case of inflammation slowly increasing with things like stress."And while diet can play a key role for many people when it comes to dealing with symptoms, Natalie says stress is a major part of the equation.
"I know that with my chronic fatigue clients, it's often about managing their stress more so than anything else. It's such a huge trigger. Stress can suppress what is known as our T-helper cells, which are linked to our immunity cells. Long-term high levels of cortisol can cause a lot of problems.
"It's hard to talk about autoimmune disorders in general terms, but I think all of the most common autoimmune issues can benefit from reducing the inflammatory load, limiting stress, and making sure we have a diet that is high in antioxidant-rich wholefoods."
Eating to reduce inflammation
Nutritionist Natalie Brady says a diet rich in anti-inflammatory foods can be a key piece of the puzzle when it comes to managing the symptoms of autoimmune illness. Here's what to look out for:
Bright coloured foods:
Highly coloured fruits and vegetables are packed with antioxidants, which have anti-inflammatory benefits, help to protect against free radical damage, and 'mop up' oxidative stress in the body. Darkly pigmented foods, such as berries and beetroot, are particularly high on the antioxidant scale.
Nuts are a great addition to any diet, but walnuts pack the biggest health punch when it comes to reducing inflammation.
Leafy green vegetables
As well as being loaded with nutrients, leafy greens help to support our liver detoxifying pathways, which is an important step for reducing inflammation. Broccoli is particularly helpful as it contains sulforaphane, an antioxidant that boosts liver detoxifying enzymes.
The main active ingredient in turmeric is curcumin, which has proven detoxifying effects. Turmeric is best eat in fresh root form - grate it into stir-fries, curries, soups and smoothies.
While a wholefoods approach is the best place to start, certain types of probiotics and fish oil supplements can have great health benefits. As the quality of supplements varies hugely, it pays to get some expert advice to point you in the right direction.
Omega 3 fatty acids found in oily fish not only boost heart, brain and joint health, they also act as a powerful anti-inflammatory. The highest levels of omega 3 are found in salmon, mackerel and sardines.
Due to the high levels of good bacteria, fermented fare like sauerkraut and kimchi have well-known gut health benefits. The bacterial strain Lactobacillus rhamnosus GG is especially helpful for reducing gut and intestinal permeability, an issue that can go hand-in-hand with autoimmune illness.