Peanuts are one of the most allergenic foods, and peanut allergy is one of the most common food allergies. Peanuts are probably the most common cause of death by food anaphylaxis in the United States, and about one third of peanut-sensitive patients have severe reactions to peanuts.
Peanuts are added to a large variety of processed foods (see first table). These include ice cream (as a flavoring), marinades, snack foods and biscuits. Peanuts can be used as a flavoring or a seasoning agent and may be labeled as such (see second table). Peanuts may be used in the manufacture of vegetable burger patties. A fatal reaction to peanut antigens in almond icing has been recorded. Peanut butter may also be used to glue down the ends of egg rolls to keep them from coming apart. Additionally, it is not widely known that peanut butter is commonly used in Asian cuisine. Peanuts can be deflavored, reflavored, and pressed into other shapes such as almonds and walnuts. These products retain the allergenicity of the peanut. Some patients with peanut allergy also react to sweet lupine seed flour, which may be used, for example, to fortify pasta.
Foods that may contain peanut or peanut oil
- Baked goods
- Baking mixes
- Battered foods
- Breakfast cereals
- Cereal-based products
- Chinese dishes
- Egg rolls
- Ice cream
- Milk formula
- Peanut butter
- Satay sauce and dishes
- Thai dishes
- Vegetable fat
- Vegetable oil
Although uncommon, a peanut protein hydrolyzate may also be used in soft drinks as a foaming agent or in confections as a whipping agent.
Peanut oil is frequently used in the preparation of health foods. The oil can be used for many non-food products, which may, on contact, affect sensitive individuals. Like peanut oil, other vegetable oils such as soy, maize, sesame and sunflower oils contain very low quantities of protein.
Peanut oil has been considered to be devoid of allergenicity, and this was initially confirmed by double-blind crossover studies. However, peanut oil allergenicity is clearly process-related, because cold-pressed peanut oils may contain peanut allergen. Moneret-Vautrin et al. confirmed the allergenicity of peanut oil in milk formulas, and 11 of 45 brands of milk formulas in France contained variable amounts of peanut oil. Residual peanut proteins are believed to become more allergenic with heating.
A recent study showed that 50% of individuals allergic to peanuts (a legume) reported allergic reactions to other tree nuts as well, often because the foods are processed and shipped together. These findings were not validated by further clinical investigation. For patients whose allergies are limited to peanuts, nuts such as almonds, pecans, or walnuts can be used as a substitute.
Both ImmunoCAP and epicutaneous testing can help confirm peanut allergies in patients.