Chili oil is typically red in color. It is made from vegetable oil, often soybean oil or sesame oil, although olive oil or other oils may be used. Other spices may be included such as Sichuan pepper, garlic, or paprika. (Warning: if garlic is used, the shelf life is significantly shortened because the anaerobic conditions in the oil can lead to germination of Clostridium botulinum, found naturally in soil, which could then lead to botulism in the consumers of the chili oil.) The spices are soaked in oil. Commercial preparations may include other kinds of oil, water, dried garlic, soy sauce, and sugar. Recipes targeted to Western cooks also suggest other popular oils such as rapeseed, grapeseed or peanut, and any dried or fresh chili peppers. The solids typically settle to the bottom of the container in which it is stored. When using chili oil, the cook or diner may choose how much of the solids to use; sometimes only the oil is used, without any solids.
Chili oil is commercially available in glass jars, although it may also be made from scratch at home. It is usually available by request at Chinese restaurants.
The Japanese variety of Chinese chili oil is known as rāyu(ラー油 or 辣油?), used in Japan as a cooking ingredient or as a condiment. The default kind is typically a clear, chili-infused sesame oil, and the chopped chili pepper used is typically red, imparting a reddish tint to the oil. Other ingredients used may include soy oil, corn oil, dried aloe, ginger, guava leaves, leek leaves, paprika, and turmeric.
Beginning in 2009, a new type of product known as taberu rāyu(食べるラー油 or -辣油?, literally, "rāyu for eating") became a trend in 2010. This variety is known for reduced spiciness, and in addition to the usual oil, chunks of food are included such as fried garlic and fried onion. However, the variety that includes food in the chili oil, as noted above, has existed in China since ancient times.
The Italian variety of chili oil (Olio di peperoncino) originates from the southern region of Calabria. This variety of chili oil uses olive oil as a base, and has a unique brine flavor. It is unknown how long this oil has been in production, but it is assumed since the Spanish had retrieved the chili pepper from the Americas.