What is side effect of aspirin?

Aspirin side effects
Get emergency medical help if you have signs of an allergic reaction to aspirin: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Aspirin may cause serious side effects. Stop using this medicine and call your doctor at once if you have:

ringing in your ears, confusion, hallucinations, rapid breathing, seizure (convulsions);

severe nausea, vomiting, or stomach pain;

bloody or tarry stools, coughing up blood or vomit that looks like coffee grounds;

fever lasting longer than 3 days; or

swelling, or pain lasting longer than 10 days.

Common side effects of aspirin may include:

upset stomach;
heartburn;
drowsiness; or
mild headache.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Source: https://www.drugs.com/aspirin.html