Asthma is a common condition, affecting approximately 7% of people worldwide. However, the prevalence varies among countries, and in Australia, asthma affects 10% of adults and approximately 20% of children. For some of these patients, ingredients in some over-the-counter analgesics may pose problems. Aspirin sensitivity, defined as urticaria, angioedema, or rhinitis after aspirin ingestion, affects only 0.3% of the general population. However, certain patient groups, such as asthmatics, are at an increased risk, with reports of an incidence as high as 20% in this patient population. This phenomenon is not restricted to aspirin, as all nonsteroidal anti-inflammatory drugs (NSAIDs) that inhibit the enzyme cyclooxygenase display a high incidence of cross-sensitivity. In contrast, paracetamol (acetaminophen) is well tolerated by the majority of people with asthma and is seldom associated with cross-sensitivity. Determining who is likely to be affected is difficult because the sequence of symptoms is hard to predict, and patients often do not associate an asthma attack with the use of aspirin or an NSAID. The only definitive way to diagnose sensitivity is by provocation tests. In view of these difficulties, it is important for health care practitioners to take a pro-active stance by asking questions to determine whether aspirin sensitivity is a problem, counseling people about the risks, and helping them make an appropriate analgesic choice.