Aspirin for fever: What you need to know

Aspirin serves many purposes, and for generations it has been used as a fever reducer. While other over-the-counter fever reducers exist on the market today, aspirin is still a common choice for adults when they come down with a fever. 

Yes, aspirin reduces fever. Also known as acetylsalicylic acid, aspirin inhibits an enzyme needed to make prostaglandins—those natural chemicals in our body that produce pain, inflammation and fever. As such, aspirin is classified as a nonsteroidal anti-inflammatory drug (NSAID). To safely use aspirin as a fever reducer for adults, read and follow the directions on the Drug Facts label. Adults should not take more than 4,000 milligrams (mg) of aspirin in a 24-hour period.

Yes, researchers have found that aspirin is just as effective as acetaminophen (Tylenol) at reducing fever.

Aspirin may cause side effects, such as:

• Nausea
• Vomiting
• Stomach upset or pain
• Heartburn

Tell your healthcare provider if any of these symptoms are severe or do not go away.

Some side effects can be serious. If the following symptoms occur, stop taking aspirin and seek medical help right away:

• Signs of an allergic reaction, like rash, hives, itching, trouble breathing or swallowing
• Signs of bleeding, like throwing up or coughing up blood, or bright red blood in stools
• Blurred or double vision
• Dizziness
  
• Rapid, deep breathing
• Ringing in the ears

This is not a complete list of side effects, and others may occur. Contact your healthcare provider if you experience any unusual problems while you are taking aspirin.

Though effective, aspirin is not for everyone. People who are allergic to aspirin should not take it. Children and teenagers younger than 18 should not take aspirin unless specifically instructed to do so by a healthcare provider, as in this age group, aspirin is linked to Reye's syndrome, a potentially fatal illness that causes brain swelling and liver damage.

Unless specifically directed by a healthcare provider, do not take aspirin for fever if:

• You have frequent heartburn, upset stomach or stomach pain and if you have or have ever had gastrointestinal bleeding, peptic ulcer disease, anemia, bleeding problems such as hemophilia, or kidney or liver disease.
• You have or have ever had asthma, frequent stuffy or runny nose or nasal polyps (growths on the linings of the nose).
• You are already taking a daily low-dose aspirin regimen as prescribed by your healthcare provider. Instead, consider a non-NSAID medicine, such as acetaminophen (Tylenol), to reduce fever.
• You are pregnant, trying to get pregnant or are breastfeeding.
• You are having surgery, including dental surgery.
• You consume three or more alcoholic drinks every day.

There may be other reasons you should not take aspirin.

For many adults, aspirin can be a safe and effective fever reducer. If you have questions or concerns about taking aspirin, ask your healthcare provider or pharmacist.

Updated September 2024.