The Science of Inflammation: What It Is, Why It Hurts, and What Helps

Last updated: October 2026.

Inflammation has become a buzzword. It is blamed for everything from tiredness to sore joints, and countless products claim to “fight” it. But inflammation is not the enemy. It is one of the body’s most important defence and repair systems, and without it you would not survive a cut finger.

This guide explains what inflammation actually is, why it sometimes causes pain, the difference between short-term and long-term inflammation, and the everyday habits that research links with a healthier balance.

The short answer

• Inflammation is the immune system’s response to injury or infection. In the short term it protects you and helps healing.
• Acute inflammation causes redness, heat, swelling and pain, and usually settles in days.
• Low-grade chronic inflammation is linked with inactivity, excess weight, smoking, poor sleep and diets high in ultra-processed food.
• Regular movement, a plant-rich diet, good sleep, not smoking and limiting alcohol are the habits with the best evidence.

Important: this is general information, not medical advice. If you live with pain, work with your GP or a pain specialist. Seek urgent help for sudden severe pain, chest pain, or pain with weakness, numbness, or loss of bladder or bowel control.

What is inflammation?

When tissue is injured or infected, the immune system sends in a rapid response team. Blood vessels widen to bring more blood to the area, and become leakier so that immune cells and proteins can reach the tissue. White blood cells clear away germs and damaged cells, and repair begins.

This process is coordinated by chemical messengers, including histamine, prostaglandins and cytokines. Some of these messengers also make nerve endings more sensitive, which is why inflamed areas hurt. That sensitivity is useful: it encourages you to protect the injured area while it heals.

The five classic signs

Doctors have described the signs of acute inflammation for nearly two thousand years:

Sign	Latin term	Why it happens
Redness	Rubor	Increased blood flow
Heat	Calor	Increased blood flow and metabolic activity
Swelling	Tumor	Fluid and cells leaking into tissue
Pain	Dolor	Chemical messengers sensitise nerves
Loss of function	Functio laesa	Pain and swelling limit movement

Acute vs chronic inflammation

Acute inflammation

Acute inflammation is fast and short-lived. A sprained ankle, a sore throat or a splinter all trigger it. It usually peaks within a day or two and settles as healing progresses. This is healthy and necessary.

Chronic inflammation

Sometimes inflammation does not switch off properly. Chronic inflammation can be part of specific conditions, such as rheumatoid arthritis, inflammatory bowel disease or psoriasis, which need medical diagnosis and treatment. There is also a less visible “low-grade” inflammation, measurable in blood tests, that researchers have linked with lifestyle factors and with a higher risk of long-term conditions such as heart disease and type 2 diabetes.

Inflammation and pain

Not all pain is caused by inflammation, and not all inflammation causes pain. Pain is produced by the nervous system, and it can be influenced by many factors, including sleep, stress, mood and past experiences. In persistent pain, the nervous system itself can become more sensitive, so pain continues even after tissue has healed. This is why understanding pain usually requires a broader view than inflammation alone. Our article on pain and mental health explores this.

Lifestyle factors linked with low-grade inflammation

• Inactivity. Long periods of sitting are linked with higher inflammatory markers; regular activity with lower ones.
• Excess body fat. Particularly around the waist, fat tissue releases inflammatory messengers.
• Smoking. One of the strongest lifestyle drivers of inflammation.
• Diet. Diets high in ultra-processed foods, sugary drinks and processed meats are associated with higher inflammatory markers.
• Poor sleep. Short or disrupted sleep is linked to raised inflammatory markers.
• Chronic stress. Long-term stress affects immune regulation.
• Alcohol. Heavy drinking is associated with inflammation, particularly in the gut and liver.

Habits with the best evidence

Move regularly

Regular physical activity has some of the most consistent evidence for lowering inflammatory markers over time. Aim for the HSE guideline of at least 150 minutes of moderate activity a week, such as brisk walking, cycling or swimming, plus strength exercises twice a week.

Eat a Mediterranean-style diet

Diets rich in vegetables, fruit, whole grains, beans, nuts, olive oil and oily fish are associated with lower inflammatory markers in research. In Irish terms, that might mean porridge with berries, more beans and lentils in stews, oily fish such as mackerel or salmon twice a week, a handful of nuts as a snack, and plenty of vegetables with every meal.

Sleep well

Aim for consistent sleep and wake times. Our guide to the circadian rhythm explains how.

Stop smoking and limit alcohol

The HSE QUIT service offers free support to stop smoking. For alcohol, keep within the low-risk guidelines: less than 11 standard drinks a week for women and less than 17 for men, with alcohol-free days.

Manage stress

Regular movement, time outdoors, social connection, and techniques such as slow breathing or mindfulness all help. See our breathing techniques guide.

A week of inflammation-friendly meals

You do not need special foods or expensive powders. Small swaps in an ordinary Irish diet go a long way:

Meal	Simple swap
Breakfast	Porridge with frozen berries and a spoon of seeds instead of sugary cereal
Lunch	Wholegrain bread or a bean soup instead of white bread and processed meats
Snack	A handful of nuts or a piece of fruit instead of biscuits
Dinner	Baked mackerel or salmon twice a week, with plenty of vegetables
Cooking	Olive or rapeseed oil instead of butter for most cooking
Drinks	Water, tea or coffee instead of sugary drinks; alcohol-free evenings in the week

Irish rapeseed oil is a good, locally produced choice for cooking and is lower in saturated fat than butter. Frozen fruit and vegetables are just as nutritious as fresh and help reduce waste.

Inflammation after exercise

If you are sore a day or two after a new workout, that is usually delayed onset muscle soreness (DOMS), a normal part of muscles adapting. It typically peaks 24 to 72 hours after exercise and settles on its own. Gentle movement, a good night’s sleep, staying hydrated and building up training gradually are the best approaches. Many athletes also use heat, massage and topical products as part of their recovery routine. Sharp pain, significant swelling or pain that does not improve after a week should be checked by a GP or physiotherapist.

What about supplements and CBD?

Many supplements are marketed as “anti-inflammatory”. The evidence for most is limited, and none should replace medical treatment for an inflammatory condition. Omega-3 fatty acids from oily fish have been widely studied. Researchers are also interested in how CBD and other compounds from hemp interact with the immune system, but this research is mostly in the laboratory and in animals. CBD sold as a food supplement in Ireland is not intended to treat, prevent or reduce inflammation or any condition, and we make no such claims.

Some people choose CBD products such as our CBD Muscle & Joint Cream or CBD Oil 10% as part of a general wellness routine. If you do, check with your GP or pharmacist first if you take medication, especially blood thinners or anti-inflammatory medicines.

When to see your GP

• Joint pain, swelling or stiffness lasting more than a few weeks, especially morning stiffness over 30 minutes.
• Swelling, redness and heat in a joint with fever: seek same-day advice.
• Ongoing digestive symptoms such as diarrhoea, blood in the stool or abdominal pain.
• Persistent skin rashes, unexplained fevers, weight loss or fatigue.

Frequently asked questions

Is inflammation good or bad?

Both. Short-term inflammation protects you and helps healing. Long-term, low-grade inflammation is linked with lifestyle factors and some long-term health conditions.

What causes chronic inflammation?

Specific medical conditions, as well as lifestyle factors such as inactivity, smoking, excess weight, poor sleep, chronic stress and diets high in ultra-processed foods.

What foods are linked with lower inflammation?

Mediterranean-style diets rich in vegetables, fruit, whole grains, beans, nuts, olive oil and oily fish are associated with lower inflammatory markers.

Does CBD reduce inflammation?

Research is mainly in the laboratory and in animals. CBD food supplements are not intended to treat or reduce inflammation, and we make no such claims.

Does exercise cause inflammation?

Exercise causes short-term inflammation as muscles adapt, but regular exercise is linked with lower inflammation over time.

How is inflammation measured?

Blood tests such as CRP (C-reactive protein) can measure inflammation. Your GP will decide whether testing is appropriate.

Should I take anti-inflammatory painkillers regularly?

Only as advised by your doctor or pharmacist. Long-term use of NSAIDs such as ibuprofen can cause side effects.

What is DOMS?

Delayed onset muscle soreness is the normal stiffness and soreness you can feel 24 to 72 hours after new or intense exercise. It settles on its own.

Disclaimer: CBD is sold as a food supplement. It is not intended to diagnose, treat, cure or prevent any disease and is not a substitute for medical advice. Always consult a healthcare professional before starting a new supplement, especially if you take medication, are pregnant or breastfeeding.