Short answer: Dahi (curd) is not inherently disallowed in Jainism, but it is a debated topic because of ahimsa (non-violence) toward tiny life-forms in fermented foods.

• Why some Jains avoid it: Fermentation involves bacteria and other microorganisms that are living beings. Many Jains consider consuming foods with a high amount of living microbes to cause more hiṃsā (violence) than fresh, non-fermented foods.
• Why some still eat it (with conditions): Some devotees allow only freshly set curd, made from boiled milk and eaten within a short time, to minimize harm. Fresh curd is seen as less harmful than older, more strongly fermented products.
• Variation between traditions: Digambar and Śvetāmbara communities may have different practical rules. In practice, many Śvetāmbara Jains are more flexible about curd, while stricter followers (often among both traditions) may avoid it on certain days or periods.
• Other fermented foods: Most Jains avoid other fermented items and aged foods, but preferences can vary by individual and local practice.

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