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Acetylcysteine

Acetylcysteine Side Effects

Kristianne Hannemann, PharmDDaisy Chau, PharmD
Reviewed by Kristianne Hannemann, PharmD, Daisy Chau, PharmD
Last reviewed on October 31, 2025

The following side effects may get better over time as your body gets used to the medication. Let your healthcare provider know immediately if you continue to experience these symptoms or if they worsen over time.

Common Side Effects

Less Common Side Effects

  • Mouth sores
  • Nausea
  • Vomiting
  • Fever
  • Runny nose
  • Drowsiness
  • Clamminess
  • Chest tightness

Acetylcysteine serious side effects

Contact your healthcare provider immediately if you experience any of the following.

  • Tightening of the airways: trouble breathing, wheezing, coughing, chest tightness

Source: DailyMed

The following Acetylcysteine side effects have also been reported

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

Less common

Wheezing, tightness in chest, or difficulty in breathing (especially in asthma patients)

Rare

Skin rash or other irritation

Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

Less common

Clammy skin

fever

increase in amount of mucus in lungs

irritation or soreness of mouth, throat, or lungs

nausea or vomiting

runny nose

For patients using a face mask for inhalation of acetylcysteine: the mask may leave a stickiness on your face. This can be removed with water.

When you use acetylcysteine, you may notice that the medicine has an unpleasant odor at first. However, this smell will go away soon after you use the medicine.

Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

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Why trust our experts?

Kristianne Hannemann, PharmD, is a licensed pharmacist in California. She has been a retail pharmacy manager and staff pharmacist for over 7 years and has contributed drug information content to different health companies.
Daisy Chau, PharmD
Reviewed by:
Daisy Chau, PharmD
Daisy Chau, PharmD, is the drug information pharmacist manager at GoodRx. She is licensed in California and has more than 6 years of experience working as a pharmacist in drug information.

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