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Aspirin, Inflammation, and COX Enzymes: Facts and Effects

Linda Crampton is an experienced teacher with a first-class honors degree in biology. She writes about the scientific basis of disease.

Willow trees contain salicin, which is related to aspirin.

Willow trees contain salicin, which is related to aspirin.

A Useful Medication With Some Drawbacks

When aspirin was first created, it was hailed as a wonder drug for inflammation, pain, and fever. It's still a very useful medication. It has many health benefits and is a staple in many people's medicine cabinets. Some people have moved to a different medication because aspirin has drawbacks as well as advantages, however.

Aspirin relieves inflammation due to its ability to inhibit an enzyme in the body called COX-2. Unfortunately, aspirin also inhibits the COX-1 enzyme. This inhibition can lead to stomach irritation and bleeding problems. Aspirin increases bleeding by decreasing the formation of blood clots. The reduction of blood clots may actually be helpful in people with cardiovascular disease. The medication may also be helpful in reducing the risk of some types of cancer, although this benefit is still being investigated.

The information in this article is given for general interest. A doctor should be consulted if someone has a chronic health problem and wants to take aspirin or if they want to take the drug frequently, for a long time, or at high doses. Aspirin mustn't be given to children without a doctor's recommendation. The reason is given later in this article.

A weeping willow tree in the spring

A weeping willow tree in the spring

Salicin in Willow Bark

Aspirin is chemically related to salicin, a chemical found in the inner bark of willow trees and also in some other plants. Willow bark has been used to treat pain and fever since ancient times. Salicin is turned into salicylic acid in our digestive tracts.

In the 1800s, scientists isolated salicin from willow trees. They converted it to salicylic acid, which was used as a medicine. The acid often caused severe stomach pain, however. German chemist Felix Hoffmann worked for the Bayer company and is credited with the creation of aspirin in 1897. He converted salicylic acid into acetylsalicylic acid, also known as ASA or aspirin. Aspirin was found to cause less stomach pain than salicylic acid while still relieving other body pains and fever.

Acetylsalicylic acid was given the name Aspirin, from the A for acetyl and the spirin from Spirea, the genus name for shrubs that are an alternative source of salicylic acid.

— Smithsonian Magazine, via the Science History Institute

Inflammation is a helpful process, provided it's short lived. During inflammation, white blood cells travel to the injured area to fight infection.

Inflammation is a helpful process, provided it's short lived. During inflammation, white blood cells travel to the injured area to fight infection.

Inflammation Facts

Inflammation is a normal body response to injury. When tissue is damaged by an infection, chemicals, physical trauma, heat, or radiation, inflammation begins. Extra blood flows to the injured area. This causes fluid to leak out of the blood vessels and produces heat, redness, swelling, and pain. The blood and fluids contain white blood cells and proteins that destroy infectious organisms, such as bacteria and viruses. Inflammation helps to seal off the injured area from the rest of the body. In addition, damaged cells are destroyed and the repair of injured tissues begins.

Inflammation is uncomfortable but is normally a temporary process. This short-lived inflammatory response is known as acute inflammation. Acute inflammation subsides as pathogens are killed and body tissue is repaired. Unfortunately, acute inflammation in certain parts of the body, such as in the brain, is very dangerous. Inflammation that lasts a long time (chronic inflammation) can also be serious and may lead to a variety of health problems.

Extra blood flows through blood vessels to injured areas during the inflammatory response. Fluid from the blood leaves the capillaries and enters the tissues.

Extra blood flows through blood vessels to injured areas during the inflammatory response. Fluid from the blood leaves the capillaries and enters the tissues.

How Aspirin Reduces Inflammation

There are several versions of the COX (cyclooxygenase) enzyme. The best known forms of the enzyme are COX-1 and COX-2. COX-1 is found in most of our cells. COX-2 is much less common but is found in increased amounts in inflamed areas.

The COX enzymes stimulate the body to make chemicals called prostaglandins. Different prostaglandins produce different effects. Some maintain normal body function, but others cause inflammation, pain, and fever. COX-2 stimulates the production of inflammatory prostaglandins. Aspirin inhibits the manufacture of COX-2, thereby decreasing inflammation.

Aspirin may affect the stomach lining.

Aspirin may affect the stomach lining.

Possible Side Effects of Aspirin Use

Stomach Problems

Since aspirin inhibits the COX-1 enzyme as well as the COX-2 enzyme, it can sometimes cause problems. COX-1 stimulates the production of prostaglandins that maintain the mucus layer inside the stomach. The mucus protects the stomach lining from being attacked by the hydrochloric acid and digestive enzymes that are present in the cavity of the stomach. Without enough mucus in the stomach, a person taking aspirin may develop an inflamed stomach lining (gastritis) and ulcers (sores) on the lining.

Reduced Blood Clotting

Another function of COX-1 is to stimulate blood platelets to make thromboxane A2. This chemical triggers platelets to stick together around a wound, starting the clotting process. Since aspirin inhibits the production of COX-1, it also inhibits blood clotting. Wounds on the stomach lining and elsewhere may bleed more freely during treatment with aspirin.

Kidney Problems, Asthma, and Tinnitus

Aspirin may have other effects in the body. It may cause kidney problems, since COX-1 is needed for normal kidney function. In addition, up to twenty percent of adults with asthma experience an asthma attack when they take aspirin. Aspirin can also cause tinnitus (ringing or other sounds in the ears in the absence of external sounds) or make existing tinnitus worse.

Reye's Syndrome

In children who have experienced a recent viral disease or who have a current one, aspirin use may cause Reye’s syndrome. This is a very dangerous condition in which the brain and liver swell. It's very important that a parent or caregiver discusses aspirin use in children and teenagers with a doctor. There may not be obvious signs that a child or teen has a viral infection.

Aspirin may help to keep the heart healthy.

Aspirin may help to keep the heart healthy.

Aspirin and Cardiovascular Problems

Aspirin’s ability to reduce blood clotting can be a harmful side effect of the medication. It may be a helpful feature in some people, however. These include people at risk for developing blood clots in the heart, a condition that may cause a heart attack, or blood clots in the carotid arteries traveling up the neck to the brain, which could lead to a stroke.

Some doctors recommend that patients who have an increased likelihood of developing these disorders take a low dose of aspirin every day. It’s very important to consult a doctor before this routine is begun, however. Recently, new research has suggested that the benefits of daily aspirin depend on the age at which its ingestion is begun. In addition, the extent of the benefit may not be as great as was originally thought.

Some people with peripheral artery disease, or PAD, take aspirin to help their disorder (with their doctor’s advice). PAD usually affects arteries travelling to the legs. It's a condition in which an artery is narrowed by fatty deposits on the arterial lining. The narrowed passageway for blood flow increases the chance of blood clot formation.

If you are at risk for developing a cardiovascular problem or if you already have one, talk to your doctor about the advisability of taking aspirin. The doctor will know how the drug might affect your health and should know about the latest research. They will also be able to recommend a suitable dose if the drug is necessary.

Effect of Aspirin on Cancer Risk

Aspirin may have another possible benefit that might be related to its ability to decrease inflammation. The medication may reduce the risk of some types of cancer, especially colorectal cancer. The picture is far from clear, however. In addition, as the video below points out, we shouldn’t expect aspirin to protect us from getting cancer if we perform activities known to promote the disease, such as smoking.

In March 2015, the Fred Hutchinson Cancer Research Center published their analysis of ten large population studies. They concluded that regular aspirin intake is protective against colorectal cancer in most people. However, 9% of the people in their study who had a particular genetic makeup received no benefit from taking aspirin with respect to cancer risk. In 4% of the people with another type of genetic makeup, aspirin actually increased the risk of colorectal cancer. The center concludes that more research is needed and that they can't yet make a blanket recommendation that we all take aspirin to prevent cancer.

It will be interesting to see if researchers discover how aspirin works to protect people from cancer (if in fact it does) and whether this protection results from its ability to reduce inflammation, as has been speculated. There is evidence linking chronic inflammation to cancer development. It will also be interesting to discover why aspirin's action seems to depend on genetics.

Over-the-Counter and Prescribed NSAIDs

NSAIDs (nonsteroidal anti-inflammatory drugs) are a group of chemicals that include aspirin. Like aspirin, ibuprofen and naproxen are NSAIDs and inhibit both COX-1 and COX-2. Acetaminophen (paracetamol) is not an NSAID. It's used to treat pain and fever, but it only weakly inhibits the COX-2 enzyme and is not anti-inflammatory. Acetaminophen is believed to exert its effects by acting on the central nervous system. A person needs to seek medical advice about taking any of the medications mentioned in this paragraph in high doses or for a long time. The drugs should be kept out of the way of children and pets.

The medications mentioned above are said to be over-the-counter drugs because they can be bought without a prescription. Doctors can prescribe different NSAIDs that may be more advantageous for a patient's condition. New drugs have been created that inhibit COX-2 but not COX-1. These drugs don’t create stomach problems since they don’t inhibit the COX-1 enzyme. Unfortunately, some of them have been found to cause serious health problems, including an increased risk of heart attack, stroke, and liver damage, and have been withdrawn from the market.

An Anti-Inflammatory Diet and Inflammation

Over the long-term, an anti-inflammatory diet may help to decrease chronic inflammation and even reduce the need for certain medications. It's very important that you don't reduce the dose of a medication or stop taking it without your doctor's advice, however.

In an anti-inflammatory diet, foods that are believed to reduce inflammation are emphasized while those that are thought to increase it are avoided, or at least limited. In general, vegetables, fruits, legumes (pulses), whole grains, fish, nuts, and seeds are considered to anti-inflammatory, provided they are eaten in an unprocessed form. On the other hand, refined grains, sugar, excess saturated fats, hydrogenated fats, and alcohol are generally thought to increase inflammation.

Chronic inflammation contributes to many health problems. Some of these problems include rheumatoid arthritis, asthma, and inflammatory bowel disease. If you have a disorder that involves inflammation, it’s worth following an anti-inflammatory diet to see if it reduces your symptoms. The diet is considered to be healthy for everyone, whether or not they are experiencing inflammation.

Anyone with specific questions about an anti-inflammatory diet with respect to their life should consult a health professional, such as a nutritionist, dietitian, or physician.

Salmon is a good source of omega-3 fatty acids.

Salmon is a good source of omega-3 fatty acids.

Specific Foods That May Reduce Inflammation

Fats containing omega-3 fatty acids have been shown to reduce inflammation. Oily fish such as wild salmon and sardines are good sources of omega-3 fatty acids known as EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). Foods such as walnuts and flax seeds contain a different form of omega-3 fatty acid. Our bodies can convert this form into EPA and DHA, though in limited amounts.

Extra virgin olive oil contains oleocanthal, which can produce a stinging sensation in the throat like ibuprofen sometimes does. It also appears to lower the levels of COX-1 and COX-2 like ibuprofen, reducing inflammation. The amount of olive oil that is normally ingested each day is equivalent to a weak dose of ibuprofen, but it’s thought that over time the regular consumption of extra virgin olive oil can decrease inflammation. Other substances that are believed to reduce inflammation are green vegetables, berries, herbs, and certain spices, especially ginger and turmeric.

Berries are an important component of an anti-inflammatory diet.

Berries are an important component of an anti-inflammatory diet.

Important Medication Precautions

Don't start taking daily aspirin (or a different NSAID) for any reason without consulting your doctor. Some people experience unpleasant and potentially dangerous side effects from aspirin use. People with certain medical conditions shouldn't take the medication. In addition, certain drugs shouldn't be combined with aspirin. The dose that's taken is also an important point to consider.

It's interesting that such an old medication as aspirin can have important benefits, despite the creation of newer drugs. It's not ideal for everyone and is associated with problems as well as benefits, but for some people it's a very helpful medicine.


This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.

© 2011 Linda Crampton


Linda Crampton (author) from British Columbia, Canada on January 26, 2012:

Yes, I eat omega-3 fish, avocados and olive oil too, BlissfulWriter. I don't take omega-3 supplements because I prefer to get my good fats from food. Supplements would be good in some situations, though. Thank you very much for the visit and the comment.

BlissfulWriter on January 26, 2012:

We must have a some amount good fats everyday to keep inflammation down. I like to get them from avocados, sardines, salmon, and olives. I also take omega-3 and krill-oil supplements.

Linda Crampton (author) from British Columbia, Canada on November 26, 2011:

Thank you for the visit and the comment, Moon Willow Lake.

Moon Willow Lake on November 26, 2011:

Thank-you for this detailed information, and for describing the willow tree's part in all this.

Linda Crampton (author) from British Columbia, Canada on February 10, 2011:

Hi, breakfastpop. Thank you for your comment. You're right - aspirin is very helpful but must be used carefully.

breakfastpop on February 10, 2011:

Very informative hub. Aspirin is a miracle drug that is so often taken for granted. Of course, like anything else it must be taken properly.

Linda Crampton (author) from British Columbia, Canada on January 25, 2011:

Hi, Martie. Thanks for commenting. It’s scary how a medicine that can be so helpful can sometimes be so dangerous. Reye’s syndrome is considered to be a rare disease, but it's potentially fatal.

Martie Coetser from South Africa on January 25, 2011:

When my children were small the dangers of Aspirin were not known, and I’ve broken their fevers – in particular caused by tonsilitis – within minutes with only half of an aspro. Now I shudder when I read about the dangers. Thank heavens my children survived that. Thanks, Alicia, for this informative and excellent hub about Aspirin.

Linda Crampton (author) from British Columbia, Canada on January 24, 2011:

Hi, kashmir56. Thanks for your comment. I enjoy researching how medications work in the body.

Thomas Silvia from Massachusetts on January 24, 2011:

Hi AliciaC thank you for this great and well researched hub on aspirin . Some of it i did not know.