der Inhaltsstoff
ingredient
An individual component that a product is made of, especially in food, cosmetics, or medicines.
Ich habe eine Allergie gegen einen Inhaltsstoff in dieser Creme.
I have an allergy to an ingredient in this cream.

ingredient
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ingredient
An individual component that a product is made of, especially in food, cosmetics, or medicines.
Ich habe eine Allergie gegen einen Inhaltsstoff in dieser Creme.
I have an allergy to an ingredient in this cream.

The word is made up of 'der Inhalt' (the content) and 'der Stoff' (the substance/material). So it literally refers to a substance that makes up the contents of a product.
Der wichtigste Inhaltsstoff dieser Salbe ist Zink.
The most important ingredient in this ointment is zinc.
Common combinations are 'natürliche Inhaltsstoffe' (natural ingredients), 'künstliche Inhaltsstoffe' (artificial ingredients), or 'schädliche Inhaltsstoffe' (harmful ingredients). On packaging, you often find a 'Liste der Inhaltsstoffe' (list of ingredients).
Dieses Shampoo wirbt mit rein natürlichen Inhaltsstoffen.
This shampoo advertises that it contains purely natural ingredients.
This word is typically used for the components of industrially manufactured products, for example food, cosmetics, cleaning products, or medicines.
Manche Inhaltsstoffe in Fertiggerichten können Allergien auslösen.
Some ingredients in ready-made meals can trigger allergies.
component / part
'Bestandteil' and 'Inhaltsstoff' both refer to a part of something larger. 'Bestandteil' is more general and fits many things, for example a plan, a contract, a machine, or a text. 'Inhaltsstoff' is used mainly for products that are made by mixing substances, especially food, cosmetics, or medicines. Learners may confuse the words because an ingredient is also a component. But not every component is an ingredient. In practical terms: with cream, juice, or tablets, 'Inhaltsstoff' sounds more natural; with systems, projects, or objects, 'Bestandteil' is more likely.

Vor dem Kauf liest Anna die Inhaltsstoffe der neuen Hautcreme.
Before buying it, Anna reads the ingredients of the new skin cream.
Eine klare Kostenübersicht ist ein wichtiger Bestandteil unseres Plans.
A clear cost overview is an important part of our plan.