Introduction to Aspirin Contraindications
Aspirin, the white pill old for more than 100 years, has built its popularity as one of the most effective drugs with an anti-inflammatory effect, a painkiller, and an anti-platelet profile at the same time. (1-3)
“If we eliminated all but three drugs, aspirin would be one of the three drugs we should keep,”
said Dr. Philip Majerus, the discoverer of the preventive effect of Aspirin on heart attack and stroke. (4)
We use this effective drug mainly when we have a fever or need to eliminate a headache or backache immediately (1-2). Being confident based on its usage or only on its positive effects is not always a good idea.
Even Aspirin has side effects, and there are certain conditions when it is contraindicated. Being allergic to Aspirin and having asthma are some cases when another painkiller or fever reliever should be considered. (1-3)
This article explains when Aspirin is contraindicated and why. Keep reading to learn about contraindications and when and how to use Aspirin safely.
When Can You Use Aspirin?
Aspirin or acetylsalicylic acid inhibits cyclooxygenase-1 (COX-1) and modifies the activity of cyclooxygenase-2 (COX-2). Cyclooxygenase is an enzyme that helps in prostaglandins’ production, a substance responsible for pain. Inhibition of the COX pathway results in lipoxins production (substances with an anti-inflammatory effect) and blockage of the production of prostaglandins. (2-3)
Therefore, acetylsalicylic acid is effective in stopping inflammation and pain.
You can use acetylsalicylic acid to reduce fever and to relieve minor aches and pain that occur when you have:
- Premenstrual & menstrual cramps;
- Arthritis. (1-2)
Your doctor may also prescribe acetylsalicylic acid for symptoms relief in:
- Rheumatoid arthritis – a type of arthritis when the lining of the joints swells;
- Osteoarthritis – a type of arthritis where the lining of the joints is broken-down;
- Systemic lupus erythematosus – a condition in which the immune system attacks the joints and organs and causes pain and swelling);
and other rheumatologic conditions when the immune system attacks parts of the body. (3)
Acetylsalicylic acid blocks thromboxane, a substance that platelets release, that stimulates platelet aggregation. By that, acetylsalicylic acid effectively prevents platelets from aggregating and forming blood clots. (5)
Additionally, your doctor may recommend nonprescription Aspirin to reduce the risk of death due to a heart attack, prevent ischemic stroke (when a blood clot blocks the blood flow to the brain), or mini-strokes. (2)
When shouldn’t you use acetylsalicylic acid?
There are certain conditions when you shouldn’t use acetylsalicylic acid. Consult your doctor about a safe alternative if you find yourself in the contraindications below.
Have you ever experienced an allergic reaction to any pain reliever or fever reducer? If so, do not take acetylsalicylic acid. You may be allergic to Aspirin, too. Ibuprofen is one of them; a cross-reaction is why people allergic to ibuprofen should not take acetylsalicylic acid. (2-3)
The American Academy of Allergy, Asthma & Immunology describes the following symptoms when someone is allergic to acetylsalicylic acid:
- Shortness of breath;
- Nasal congestion;
- Feeling faint or even passing out. (6)
When these symptoms are severe, we call it anaphylaxis.
There are two major categories of allergic reactions to acetylsalicylic acid:
- About 15 % of the cases have respiratory symptoms;
- More than 75% of the cases include urticaria and angioedema.
The allergic reaction and, therefore, contraindication that some individuals have comes from Aspirin’s mechanism of action. When acetylsalicylic acid inhibits COX-1 and COX-2 enzymes, alternative metabolism of arachidonic acid takes place with the activation of lipoxygenase. As a result, the body synthesizes more leukotrienes (chemicals that the body releases when inflammation is present) that, in the end, cause bronchospasm. (7)
If you have asthma, allergic rhinitis (stuffed or runny nose frequently), or nasal polyps, there is a risk that you are allergic to acetylsalicylic acid. (1-2) So, Aspirin is contraindicated in those patients.
About 1 in 10 adults and almost 1 in 3 with asthma and nasal polyps have aspirin-exacerbated respiratory disease (AERD). This chronic medical condition usually occurs suddenly at 20 to 50 years old. (8)
Those who are sensitive to Aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs), after ingesting, may experience respiratory reactions:
- Increased nasal congestion;
- Frontal headache or sinus pain;
- chest tightness.
AEDR symptoms can also include the following:
- Skin flushing;
- Abdominal pain;
- Occasionally vomiting. (8)
Because of that, don’t take acetylsalicylic acid alone if you have asthma, rhinosinusitis, or nasal polyps. Instead, tell your doctor about your health condition and ask what medication is appropriate.
Acetylsalicylic acid may increase the risk of gastrointestinal bleeding in people with peptic ulcer disease or gastritis. The same risk is present in those who consume alcohol more than three drinks daily without stomach problems. (3)
Aspirin is a weak acid that can penetrate the gastric mucosa’s upper layer, cross the plasmatic membrane of the gastric cells, dissociate the molecules, and trap hydrogen in the cells.
The other toxic effect results from its cyclooxygenase inhibition which reduces prostaglandins synthesis; as a result, prostaglandins cannot play their protective role. Gastric epithelium secretes less bicarbonates and mucus, blood flow in the gastric mucosa is impaired, and the proliferation of epithelial cells is reduced. (9)
As a result, gastric mucosa becomes weaker, can be easily injured by body acids (pepsin and stomach acid), and cannot repair as usual. On top, the antithrombotic effect of Aspirin supports bleeding in the GI tract once it happens. This toxic effect of acetylsalicylic acid could lead to severe bleeding, ulcer perforation, and even death. (9)
Patients with hemophilia, dengue, or yellow hemorrhagic fever should also avoid Aspirin. (3)
Acetylsalicylic acid may cause Reye’s syndrome in children and teenagers, especially if the child is infected with the flu or chicken pox virus.
It is a rare but serious condition that produces swelling in different parts of the child’s body, such as the brain or liver. This results in symptoms such as confusion, seizures, and loss of consciousness. If such, emergency treatment is needed and can save a life. (2, 10)
Therefore, children and teenagers recovering from chicken pox or flu-like symptoms should never use acetylsalicylic acid, although approved in children older than three years. (10)
Recommended Aspirin Dosage
Aspirin is available in different formulations:
- Regular tablets or liquid capsules;
- Extended-release tablets – duration of the medication activity is longer than the regular;
- Delayed-release tablets – the active ingredient is released in the intestine that prevents possible damage in the stomach. (2)
Therefore, it is essential to read the directions on the OTC pack carefully and follow the prescription instructions given by the doctor who prescribed your Aspirin.
Adults and children over 12 years can use Aspirin. The recommended dose is 1 to 2 capsules or tablets of 325 mg every 4 hours. When symptoms persist, you can take 3 capsules every 6 hours. Do not take more than 12 capsules in 24 hours. (1)
If you have a child younger than 12, consult a doctor before giving Aspirin. (1)
Side effects and warnings
Aspirin is a well-established medication, and its side effects are already known. Nausea, vomiting, stomach pain, or heartburn might appear; however, you should tell your doctor if these symptoms are severe. (2)
Call your doctor immediately in the following conditions:
- You may experience hives, facial swelling, low blood pressure, or wheezing in case of allergic reactions;
- If you notice bloody vomit, vomit that looks like coffee grounds, bright red blood in stools, or black or tarry stools as possible symptoms of severe stomach bleeding associated with NSAIDs, including Aspirin;
- Changes in behavior with nausea and vomiting could be early signs of Reye’s syndrome;
- Fast heartbeat, fast breathing, cold, clammy skin, ringing in the ears, or loss of hearing.
Despite being over 100 years used effectively by many generations and known as a magic pill, Aspirin is contraindicated in those who are allergic to Aspirin or another NSAID painkiller. Also, don’t use it if you have stomach problems; consult your doctor.
Ask your doctor what is the best fever reliever for your child, especially if your child recovers from a virus infection.
As with any other medication, read the label before taking Aspirin. Then’ follow directions by the manufacturer of the OTC product and use it as your doctor prescribed.
You can report any adverse event to your doctor or the Food and Drug Administration’s (FDA) MedWatch Adverse Event Reporting program online (http://www.fda.gov/Safety/MedWatch) or by phone (1-800-332-1088). (1-2)
Use Aspirin with caution and kill your pain safely.
1. Food and Drug Administration, Aspirin capsules 325mg (NSAID), 2013 Jan,
2. MedlinePlus, Aspirin, 2021 May,
3. National Library of Medicine, Salicylic Acid (Aspirin), 2022 Jul,
4. Washington University in St.Louis, Aspirin, the mighty drug, 2007 Jul,
5. D. Rucker, A. S. Dhamoon. Physiology, Thromboxane A2, 2022 Sep,
6. American Academy of Allergy, Asthma & Immunology, Is it Possible to be Allergic to Aspirin? 2020 Sep,
7. D Schiavino, E Nucera, A Milani, M Del Ninno, A Buonomo, J Sun, G Patriarca, The aspirin disease, Thorax 2000;55 (Suppl 2): S66–S69
8. American Academy of Allergy, Asthma & Immunology, Aspirin-Exacerbated Respiratory Disease (AERD), 2020 Sep,
9. C. J. Lavie MD, C. W. Howden MD, J. Scheiman MD, J. Tursi MD, Upper Gastrointestinal Toxicity Associated With Long-Term Aspirin Therapy: Consequences and Prevention, Curr Probl Cardiol 2017;42:146–164
10. Mayo Clinic, Reye’s syndrome, 2023 Feb,