Chitosan is a fibre supplement and clarifier made, most of the time, from crushed shellfish shells. A newer fungal version is genuinely vegan, but it is the exception.
Usual sourceShrimp and crustacean shells
Vegan versionFungal chitosan
VerdictUsually not vegan
Where it hides
Weight-loss and fibre supplements
Wine and juice fining
Some wound dressings
Seed and food coatings
What it is
Chitosan is a fibre made from chitin, the tough material in shells and exoskeletons. Its everyday source is the seafood industry.
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It is made by treating the chitin shells of shrimp and other crustaceans with an alkaline substance, such as sodium hydroxide.
Chitin is also found in the cell walls of fungi, and a small number of producers now make chitosan from mushrooms and other fungi. That version is vegan, but it is not the default, so unless a product says fungal or vegan chitosan, assume the shellfish source. As a wine and juice fining agent, chitosan is one of the plant-adjacent finings that can replace isinglass, though only the fungal grade is vegan.
GlucosamineThe joint supplement most people reach for is usually built from crab and shrimp shells. A corn-fermented vegan version exists, but it is the exception, so the default bottle is off the menu.
IsinglassIsinglass is fish. It is a collagen made from dried swim bladders and used to clarify some beers and wines, which is why a plain-looking pint can fail the vegan test.
WineWine is grapes, but the way it is clarified is the catch. Many bottles are fined with fish, egg, milk or gelatin, others with clay or plant protein, and the label almost never tells you which.
Frequently asked
Is chitosan always from shellfish?
Not always, but usually. The standard commercial source is shrimp and crab shells. A fungal version made from mushrooms is vegan and is labelled as such.
Is shellfish chitosan suitable for a shellfish allergy?
That is a safety question rather than a vegan one, and people with a shellfish allergy should be cautious and seek the fungal version or medical advice. Either way, shellfish-derived chitosan is not vegan.
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