[2] Modern American chicken soup, which typically includes root vegetables such as carrot, onion, leeks and celery, was a staple across Northern Europe and was brought to the United States by immigrants.

[4][5] The soup should be brought slowly to a boil and then simmered in a covered pot on a very low flame for one to three hours, adding water if necessary.

[13] In 2000, scientists at the University of Nebraska Medical Center in Omaha studied the effect of chicken soup on the inflammatory response in vitro.

They found that some components of the chicken soup inhibit neutrophil migration, which may have an anti-inflammatory effect that could hypothetically lead to temporary ease from symptoms of illness.

The New York Times reviewed the University of Nebraska study, among others, in 2007 and concluded that "none of the research is conclusive, and it is not known whether the changes measured in the laboratory really have a meaningful effect on people with cold symptoms.

"[15] It has also been shown that chicken soup contains the amino acid cysteine, which is very similar to acetylcysteine, which is used by doctors for patients with bronchitis and other respiratory infections.

Typical Chinese chicken soup is made from old hens and is seasoned with ginger, scallions, black pepper, soy sauce, rice wine and sesame oil.

[20] A more elaborate version can be made from freshly killed spent hen and various herbs such as ginseng, dried goji, and old ginger root.

[22] Along with chicken, ajiaco typically includes maize, three types of potatoes, avocado, capers, and a herb called guascas, and is served with a dollop of cream.

Vegetables like celeriac, carrots, onions and leek are usually added and typical flavourings are thyme, laurels and white pepper.

As part of traditional housekeeping, the cooked meat is reserved for other dishes such as høns i asparges ("hens in asparagus") or hønsesalat ("hens-salad").

Typical French seasonings for chicken soup includes: bay leaves, fresh thyme, dry white wine and garlic.

[28] In Greece, chicken soup is most commonly made in the avgolemono ("egg-lemon") fashion, wherein beaten eggs mixed with lemon are added to a broth slowly so that the mixture heats up without curdling, also adding rice or pasta like kritharáki ("little barley;" orzo), resulting in a thicker texture; it is a traditional remedy for colds, stomach aches, and hangovers.

After the dashi is prepared, pieces of boneless chicken thigh meat are usually used and combined with vegetables like daikon radish, carrot, burdock, konnyaku, welsh onion, mushrooms, potatoes, and taro root.

[46] Another variation of chicken soup is caldo tlalpeño which is garnished with chopped avocado, white cheese, and a chipotle chile.

While there are many variations in the recipe, it usually contains chicken strips in broth, onions, vegetables (mainly carrots, cabbage and celery), and macaroni noodles.

Sinampalukang manok is sometimes regarded as a chicken version of sinigang, but here the meat is browned first before being boiled in the water and it uses tamarind leaves.

[60] East Slavs traditionally prefer an often simple chicken and vegetable bouillon with added noodles or rice, and a pinch of fresh herbs.

However, a thick, creamy variety called cream of chicken soup,[62] which may not contain any vegetable pieces (depending on the recipe), is more popular today.

A distinct version from Scotland that has become popular throughout the UK is cock-a-leekie soup, a clear, thin broth of shredded chicken and leeks.

[9] Traditionally, American chicken soup was prepared using old hens too tough and stringy to be roasted or cooked for a short time.

This gives a 1+1⁄2 cup bowl of soup[66] about 2,500 mg of sodium, a full day's allowance in the case of this mainstream brand.

[65] Campbell's claims production of a chicken noodle soup that will find broad consumer acceptance—in short, that will sell—is very difficult, so it has to balance healthfulness with sodium content.