As it is difficult to test for an allergic reaction to aspirin, the most definitive way to determine a problem is by ingesting the drug. The symptoms of an aspirin allergy depend upon the severity of the reaction. A mild reaction can include hives, itchiness, and red eyes. More severe reactions can cause breathing difficulties, swelling in the areas above the neck, and chest pain. Most symptoms of an aspirin allergy will appear within hours of taking the drug.

Some allergists can determine if there is an allergy by administering the drug in a controlled clinical procedure known as an oral challenge. The patient may be given a placebo in addition to the actual drug in order to ensure that the reaction is genuine. In some cases, the doctor may not even know which pill is the placebo during the test.

Symptoms of a mild aspirin allergy tend to be more irritating than life-threatening. In addition to the itch, hives, and redness of the eyes, patients can experience cold-like symptoms such as a runny nose or nasal congestion. Uriticaria, also known as chronic hives, can also develop. These symptoms usually go away within a few days if the patient stops using the drug.

The symptoms of a severe aspirin allergy will often require immediate medical attention. Patients can experience swelling of the eyes, lips, face, and tongue. In addition to other breathing problems, some individuals also have severe wheezing. Other serious symptoms can include chest pain, vomiting, low blood pressure, and fainting. More severe hives may also develop.

Individuals with asthma, chronic sinusitis, or nasal polyps are at a higher risk of having an allergic reaction to aspirin, though they do not necessarily need to avoid the drug. In addition to being a symptom of an allergic reaction to aspirin, a previous case of uriticaria can also increase the chances of a reaction. Patients with one of these pre-existing conditions may experience an increase in symptoms in addition to the reaction to the aspirin.

An aspirin allergy may indicate an overall allergy or sensitivity to nonsteroidal anti-inflammatory drugs (NSAIDs), which have many of the same properties. Drugs in this group include naproxen and ibuprofen. If an allergy to aspirin is already known, patients should consult a doctor before taking an NSAID. Any previous sensitivity to NSAIDs should be disclosed to a doctor before taking aspirin as well.