Aspirin should not be given to a child or teenager who has a fever, especially if the child also has flu symptoms or chicken pox. Aspirin can cause a serious and sometimes fatal condition called Reye's syndrome in children.

Stop using this medication and call your doctor at once if you have any symptoms of bleeding in your stomach or intestines. Symptoms include black, bloody, or tarry stools, and coughing up blood or vomit that looks like coffee grounds.

Avoid drinking alcohol while you are taking this medication. Alcohol may increase your risk of stomach bleeding.

Aspirin is sometimes used to treat or prevent heart attacks, strokes, and chest pain (angina). Aspirin should be used for cardiovascular conditions only under the supervision of a doctor.

Do not use this medication if you are allergic to aspirin, or if you have:

• a recent history of stomach or intestinal bleeding;
• a bleeding disorder such as hemophilia; or
• an allergy to an NSAID (non-steroidal anti-inflammatory drug) such as Advil, Motrin, Aleve, Orudis, Indocin, Lodine, Voltaren, Toradol, Mobic, Relafen, Feldene, and others. 
• if you are a child or teenager with influenza (flu) or chickenpox;
• have bleeding problems such as hemophilia, von Willebrand disease, or low blood platelets;
• you have active severe bleeding;
• you have had a severe allergic reaction (eg, severe rash, hives, breathing difficulties, dizziness), to aspirin, salicylates (e.g., salsalate), tartrazine, or an NSAID (e.g., ibuprofen, naproxen, celecoxib).

If you have any of these other conditions, you may need a dose adjustment or special tests to safely take aspirin:

• asthma or seasonal allergies;
• stomach ulcers;
• liver disease;
• kidney disease;
• a bleeding or blood clotting disorder;
• heart disease, high blood pressure, or congestive heart failure;
• gout; or
• nasal polyps

If you are taking aspirin to prevent heart attack or stroke, avoid also taking ibuprofen (Advil, Motrin). Ibuprofen may make this medication less effective in protecting your heart and blood vessels. If you must use both medications, take the ibuprofen at least 8 hours before or 30 minutes after you take the aspirin (non-enteric coated form). This medication may be harmful to an unborn baby's heart, and may also reduce birth weight or have other dangerous effects. Tell your doctor if you are pregnant or plan to become pregnant while you are taking this medication. Aspirin can pass into breast milk and may harm a nursing baby. Do not use this medication without telling your doctor if you are breast-feeding a baby.

Do not use any other over-the-counter medication without first asking your doctor or pharmacist. Aspirin is contained in many medicines available over the counter. If you take certain products together you may accidentally take too much aspirin. Read the label of any other medicine you are using to see if it contains aspirin.

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat. Stop using aspirin and call your doctor at once if you have any of these serious side effects:

• black, bloody, or tarry stools;
• coughing up blood or vomit that looks like coffee grounds;
• severe nausea, vomiting, or stomach pain;
• fever lasting longer than 3 days;
• swelling, or pain lasting longer than 10 days; or
• hearing problems, ringing in your ears.

Less serious side effects may include:

• upset stomach, heartburn;
• drowsiness; or
• headache

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects.