During Paryushan, Jains observe heightened spiritual discipline, including stricter dietary restrictions. Traditionally, the use of yogurt (curd, dahi) is limited or avoided during this period, especially among Shwetambar Jains, because:

1. Freshness and Microorganisms: Freshly set yogurt contains a large number of microorganisms and is considered to have more life forms (nigoda), which Jains aim to minimize harming during Paryushan.
2. Preparation Restrictions: Setting or fermenting yogurt involves leaving milk to curdle, which increases the presence of live bacteria and is generally discouraged during Paryushan.

Guidelines:

• Generally, yogurt is avoided during Paryushan, especially if it is freshly prepared.
• Some traditions allow yogurt only if it was set before Paryushan began, and only on the first day. Yogurt set or consumed after the start of Paryushan is typically not considered suitable.
• Alternative: Some Jains use buttermilk (chhaas), made from pre-Paryushan yogurt, suitably diluted and churned, as it contains fewer living organisms.

Summary:

• Best Practice: Avoid yogurt during Paryushan.
• If permitted by your tradition, only use yogurt that was set before Paryushan started, and consume it on the first day.
• Consult your family elders or local Jain monk (Sadhu/Sadhvi) for specific guidance, as customs may vary.

Always remember: The core principle is to minimize himsa (harm to living beings), especially during Paryushan.