It is a resin extracted from the sap of the roots and stems of a giant variety of Fennel plant (Ferula scorodosma syn. assafoetida.) Above ground the plant has fine leaves, and blossoms with yellow flowers. Underground, it has roots that are thick and pulpy from all the sap in them. The leaves and stem will have the same smell as the resin that is extracted from them.
The resin is harvested from plants that are at least 4 years old. Before the plant flowers that year, cuts are made in the stalk close to the ground. The sap will seep out, and coagulate into a resin. This is collected, and new cuts are made.
This goes on for about 3 months before the root dries up. But before it does, a single plant will make up to 2 pounds (900g) of the resin.
When fresh, the resin is a greyish-white. As it ages, it turns from yellow to red and finally brown.
The resin has sulphur in it, so it smells like rotten eggs. Some people say it smells as though the body of a small, dead rodent has been rotting just out of sight for a few days in a warm place. The odour truly is foul: you do question at first if you’re absolutely mad adding this to your dinner, and wonder who was the first person to think of using it. But when heated, the smell goes away and the resin develops a taste somewhere between onions and garlic.
Asafoetida is sold in blocks or pieces. Cut off what you need and crush it before using. Use in small quantities: a piece no bigger than a peppercorn will do the job.
It is also sometimes sold in a more convenient ground powder form. You only need a minute quantity of it at a time. In fact, to aid this, the powder form is often sold mixed with rice flour, so that it is easier to measure, and so that the powder won’t clump. When using a powdered form mixed with rice flour, use anywhere from a dash to half a teaspoon, depending on how much rice powder is in that particular brand.
Asafoetida is used in India by people such as Brahmins and Jains who are forbidden for religious reasons from eating onions or garlic. Brahmins won’t eat onions and garlic because they believe that the two will rile the baser passions; Jains can’t eat them because to harvest onions and garlic you have to kill the whole plant.
It is also used in the Middle East.
Most Asafoetida is grown in Afghanistan and Iran. Some is also grown in Kashmir, India.
When using asafoetida, add it at the start of cooking — at the initial sautéing or frying stage, if there is one.
A very small amount goes a long way. A few shakes is enough to flavour a pound of ground meat.
The charactestic unpleasant smell disappears in cooking.
Onion or garlic, unless you are avoiding those for religious or health reasons. Otherwise, some other strong flavouring entirely, such as celery, minced turnip, minced celerica (aka celery root), freshly grated horseradish, etc.
Asafoetida appears to be safe to use for those suffering from IBS (Irritable Bowel Syndrome) and therefore having to avoid garlic, onions and shallots; as well as to those following FODMAP diets for other reasons. In fact, there’s even some evidence potentially emerging that asafoetida might even potentially help some IBS sufferers, though this is still considered homeopathic as of 2014  .
Consumer feedback would appear to indicate that asafoetida is likely safe for those with allergies or intolerances to anything in the allium family .
You must of course consult your family physician on asafoetida use if you suffer from IBS or allium allergies or intolerances; the above information is provided only to assist discussions with your medical advisors.
Asafoetida in lump form will store indefinitely. Store in an airtight container to keep the unpleasant odour away from you and other food. Some people even put it in a plastic bag, then in a container, then in the freezer, to contain the smell. Some people say put it in your neighbour’s freezer.
Ground, can be stored for up to 1 year.
Asafoetida is native to Afghanistan and Iran. It is not native to India.
The Romans used Asafoetida.
The German name, “Teufelsdreck”, means Devil’s droppings.
Asafoetida is sometimes referred to as the silphium that the Greeks and Romans used, but it isn’t really.
The word “Asafoetida” comes from the Persian word “aza”, which means resin, and from the Latin word “foetidus”, meaning “stinking”. (We still use the word “fetid” in English.)
 Irritable Bowel Syndrome: Studied Homeopathic Remedies. NYU Langone Medical Center. http://www.med.nyu.edu/content?ChunkIID=38333. Accessed November 2014.
 Peckham, Emily J et al. A protocol for a trial of homeopathic treatment for irritable bowel syndrome. BMC Complementary and Alternative Medicine 2012, 12:212 doi:10.1186/1472-6882-12-212. Accessed November 2014 at http://www.biomedcentral.com/1472-6882/12/212
 Substitute for Onion and Garlic. Nigella Kitchen. Retrieved November 2014 from http://www.nigella.com/kitchen-queries/view/Substitute-for-Onion-and-Garlic/2525
Vanderbeek, Jennifer. Low FODMAP Living: Bye-Bye Onions and Garlic. 15 April 2013. Retrieved November 2014 from http://www.scrapsoflife.com/low-fodmap-living-bye-bye-onions-and-garlic/