Daal Chini (Cinnamon) should be avoided or used with caution in the following situations:

Pregnancy and breastfeeding: Cinnamon may stimulate the uterus and cause complications during pregnancy or breastfeeding. It's best to consult a doctor before using it.
Liver problems: Cinnamon contains coumarin, which can be toxic to the liver in large amounts. People with liver problems should avoid excessive cinnamon consumption.
Blood thinning medications: Cinnamon has mild blood-thinning properties, so it should be used cautiously if you're taking blood thinners.
Surgery: It's advisable to stop using cinnamon at least two weeks before any surgery due to its potential blood-thinning effects.
Allergies: People with allergies to cinnamon may experience skin rashes, hives, or difficulty breathing.
Diabetes: While cinnamon may help regulate blood sugar levels, it's essential to monitor them closely, especially if you're taking medication for diabetes.
Irritable Bowel Syndrome (IBS) or Acidity: Cinnamon can sometimes trigger acidity or IBS symptoms in some people. If you have these conditions, try using it in small amounts to see how your body reacts.