Aspirin & painkiller allergy


IMPORTANT The information provided is of a general nature and should not be used as a substitute for professional advice. If you think you may suffer from an allergic or other disease that requires attention, you should discuss it with your family doctor. The content of the information articles and all illustrations on this website remains the intellectual property of Dr Raymond Mullins and cannot be reproduced without written permission.


Aspirin has long been used to reduce pain from inflammation and injury, as well as fever. Originally isolated from Willow Tree Bark and other plants in the early 1800's, natural salicylates were found to be effective for the treatment of pain and fever. Unfortunately, these products were very irritating to the stomach. Later, artificial salts of these natural products were made, and found to be just as effective but with less side-effects. These days, aspirin is made synthetically, and a number of similar synthetic non-steroidal anti-inflammatory drugs (NSAIDS), have been introduced.

How do aspirin and NSAIDS work?

Compounds known as prostaglandins play an important role in tissue inflammation, pain and fever. Production of prostaglandins is inhibited by aspirin and related medications (NSAIDS), because these medications inhibit an enzyme known as cyclooxygenase-1, (COX-I). Because aspirin also inhibits the activity of blood elements known as platelets (which help clotting), aspirin also thins the blood, thus reducing the risk of heart attacks and strokes. There is also recent evidence that aspirin may even reduce the risk of bowel cancer .

All drugs are potential poisons; aspirin is no exception

Common side effects of aspirin include bruising and stomach upset (or even ulcers or bleeding from the bowel), at high dose. Very high doses may cause confusion or ringing in the ears (tinnitus). It should also be avoided in children, as aspirin can trigger a condition as Reye's syndrome, where severe liver inflammation occurs.

Aspirin and allergy

Mild to severe allergic reactions to aspirin may occur. Symptoms include flushing, itchy rashes, blocked and runny noses and severe difficulty breathing or asthma, usually within an hour of taking a tablet. When assessing reactions to aspirin or similar medications, it is useful to look for evidence of underlying disease such as hives (urticaria), nose / sinus disease or asthma. This is because the presence of some medical conditions increases the likelihood of aspirin allergy.

How common is aspirin allergy?

Normal population ~ 1%

Ongoing hives/urticaria ~ 30%

Asthma ~ 20%

Asthma /sinus disease/ polyps ~ 30%

Aspirin triad - 100% by definition

The presence of aspirin is not always obvious

Aspirin and related medicines is present in many across-the-counter pain-killers as well as various sinus tablets, medicines used to control period pain and cold & flu tablets. If you are sensitive to aspirin, you will need to carefully read medicine labels and be cautious about taking any pain-killer without talking to your doctor or pharmacist first. You also must tell your anaesthetist or surgeon if you are planning surgery.

•Cold & Flu Tablets


•Period pain and headache tablets

•Inflammatory Bowel Disease Drugs – Mesalal, Salazopyrin

•Complementary Alternative Medicines – Willow Tree Bark extract, feverfew extracts, some herbal arthritis pills

•Topical salicylates such as teething gels (Bonjela, Oral-sed Gel) or topical arthritis gels (Orudis, Dencorub, Feldene, Nurofen, Voltaren)

•Rectal suppositories. These are not normally used day-to-day, but are sometimes used at the end of an operation to reduce pain after surgery.

Injected antiinflammatory drugs like Dynastat. This is a COX-2 inhibitor

There are many brands of NSAIDS

Because there are so many brand names of the same medication, and so many types of medications available, accidental exposure to NSAIDS may occur. It is therefore important to tell your pharmacist or health professional about your sensitivity to these medicines.

Testing for drug sensitivity

The mechanism by which allergic reactions to aspirin and related pain-killers occur is uncertain. There is no reliable blood or skin allergy test which has been proven to be useful for confirming or excluding sensitivity to these medicines. A graded open challenge under strict medical supervision is the usual method. Challenge testing is not always necessary, but may be advised in some circumstances: to prove that sensitivity exists, or to prove the safety of an unrelated medicine, so that you have another drug from which to choose if you need to use a pain killer. In those with the aspirin triad, topical nasal lysine aspirin challenge is available in Sydney at a specialist ENT laboratory.

What is aspirin desensitisation?

This is useful in selected patients with the "aspirin triad", a condition in which patients suffer from aspirin allergy, nasal polyps and asthma. Even though these patients are allergic to aspirin, most can be made to tolerate high doses by starting off at a very low dose of aspirin initially and increasing it day by day. Once a higher dose is reached (generally 1 – 4 tablets/day), there is reduced production of inflammatory chemicals known as leucotrienes. As leucotrienes can worsen asthma and polyp growth,  aspirin desensitisation can reduce asthma severity, the rate of polyp regrowth, and the severity of sinusitis. The decision to undertake aspirin desensitisation is best made by an allergy specialist.

Side-effects of aspirin desensitisation

•Stomach Irritation – ulceration and bleeding at high doses

•Easy bruising – common

•Tinnitus (ringing in the ears – rare)

Reasons for undertaking aspirin desensitisation in aspirin sensitive patients

•To improve asthma control

•To reduce the severity of sinusitis/nasal polyposis

•To reduce the rate at which polyps regrow

•For patients who need to use aspirin or similar medication for treatment of heart disease or arthritis.

Management of aspirin / NSAID sensitivity

Drug allergy

Avoidance is the mainstay of management. If you are allergic to aspirin or a related drug, it is still possible to be able to tolerate another related drug. The only way to prove safety is a medically supervised challenge.

Ongoing hives

If you have on-going hives or urticaria, you should avoid aspirin and NSAIDS unless you know that you can tolerate them without a problem. If you are already taking regular aspirin (for example, to thin the blood), or a regular arthritis tablet for treatment of pain, then you do not need to stop this medicine unless their hives clearly get much worse after taking a tablet.

Acute hives/severe allergic reactions after a pain-killer

Most people with aspirin/NSAID allergy are sensitive to only one drug. Unfortunately, up to 1 in 5 may have unpredictable cross-reactive allergic responses to similar medicines. Under these circumstances, an open challenge with a completely different drug can be considered if you need to take a pain killer for treatment of pain.

“Aspirin Triad”: Aspirin sensitive asthma/ nasal polyps/ sinusitis/rhinitis

Leucotriene "blockers"/antagonists (such as Singulair / montelukast or Accolate ) or aspirin desensitisation (are useful options).

Tolerability of new COX-II inhibitors

Other painkillers inhibit an enzyme known as Cyclooxygenase II (COX-II). Many of these drugs (eg. Celebrex, Mobic) have some inhibitory reaction on COX-I as well. Whilst they cause less stomach irritation than aspirin and traditional NSAIDS, some patients will have allergic reactions to these as well. Supervised challenge can be done to prove safety. NOnetheless, most allergic to a COX-1 inhibitor can tolerate one of the COX-II drugs.

Dietary salicylates in aspirin-sensitive patients

Occasional patients who are allergic to aspirin, and have the "aspirin triad", will suffer symptoms if they eat foods that have high levels of natural salicylates. This affects the occasional patient rather than the majority, and low salicylate diets are not considered a routine part of management.


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Last reviewed 5 June 2020