Asafoetida, also known as hing, is a dark amber resin derived from the dried sap of wild fennel (Ferula asafoetida/Ferula foetida) stems and roots.
The wild fennel used to make asafoetida is mainly grown in Iran, Afghanistan, and Kashmir. The most commonly available form of the spice is compounded asafoetida, a fine powder containing 30% asafoetida resin, along with flour and gum arabic.
Asafoetida powder has a strong odor and must be stored in airtight containers to avoid contaminating other foodstuffs. It loses its smell in cooking, however, and contributes an onion-like flavor to dishes.
This spice is used as a digestive aid and in pickles. In India, it is especially used by the Brahmin caste of the Hindus and by adherents of Jainism, who are not allowed to eat onions.