Short-Term Side Effects

• People who take a chitosan supplement for up to six months may be affected by short-term side effects. These can include constipation and gas. Some users have complained of an upset stomach. These side effects are caused by the fibrous sugars found in chitosan.
  
  

Allergies to Shellfish

• It is important to remember that chitosan comes from shellfish such as shrimp, lobster and crab. People who already have an allergy to shellfish are advised to seek medical advice prior to using chitosan. Chitosan is found in the shells of shellfish and not the actual meat that is eaten.
  
  

Side Effects for Breastfeeding and Pregnant Women

• Breastfeeding and pregnant women are advised not to take chitosan because there is not enough information on the supplement to know what effects may occur if taken.
  
  

Minor Side Effects

• Minor side effects that generally are not long-lasting include rash, hives, swollen heels and headaches. Medical professionals advise users to seek medical attention and discontinue use if these minor side effects persist.
  
  

Side Effects with Other Medications

• Chitosan may have other side effects when taken with other medications. Chest pain and shortness of breath have been reported when taken with some over-the-counter or prescribed medications. People who have underlying conditions involving blood clots should not take chitosan. People who experience chest pain or shortness of breath are advised to get medical attention as soon as possible.