Physical symptoms of allergic reaction can include itchiness, hives, swelling, eczema, sneezing, asthma attack, abdominal pain, drop in blood pressure, diarrhea, and cardiac arrest.

[8][6] It is recommended that babies at high risk be given peanut products in areas where medical care is available as early as 4 months of age.

[2] A 2021 study found that prevalence of peanut allergy was 1.4–2% in Europe and the United States, increasing 3.5-fold over the past two decades.

[14] Most symptoms of peanut allergy are related to the action of immunoglobulin E (IgE)[15] and other anaphylatoxins which act to release histamine and other mediator substances from mast cells (degranulation).

Symptoms can also include mild itchiness, hives, angioedema, facial swelling, rhinitis, vomiting, diarrhea, acute abdominal pain, exacerbation of atopic eczema, asthma, and cardiac arrest.

[1][16] People with confirmed peanut allergy may have cross-reactivity to tree nut, soy, and other legumes, such as peas and lentils and lupinus.

[17] Reviews of human clinical trials report that 6–40% of people with a confirmed peanut allergy will have allergic symptoms when challenged with tree nuts or legumes.

[19][21] Oral consumption is the most common route of exposure, but topical (skin) and inhalation can also trigger minor allergic reactions.

[24] These peanut allergens mediate an immune response via release of Immunoglobulin E (IgE) antibody as part of the allergic reaction.

[24] Peanut proteins that undergo non-enzymatic changes through Maillard reactions when cooked or exposed to room temperature have an increase in AGE modifications on their structure.

[30] There is conflicting evidence on whether maternal diet during pregnancy has any effect on development of allergies due to a lack of good studies.

[33] Sensitive children may react via ingestion, inhalation, or skin contact to peanut allergens which have persistence in the environment, possibly lasting over months.

[34] Airborne particles in a farm- or factory-scale shelling or crushing environment, or from cooking, can produce respiratory effects in exposed allergic individuals.

In The Peanut Allergy Answer Book, Harvard pediatrician Michael Young characterized this secondary contact risk to allergic individuals as rare and limited to minor symptoms.

Blinded, placebo-controlled studies were unable to produce any reactions using the odor of peanut butter or its mere proximity.

[36] Rarely, allergic reactions have been triggered by exposure from kissing and sexual contact, especially if the partner has eaten peanuts within the last hour.

[37] In 2005, a "kiss of death" was misreported as being due to peanut allergy; instead, the person died of an asthma attack after smoking.

[39] The receptor-cytokine binding causes their differentiation into IgE which can then be bound onto FcεRI on mast cells, eosinophils and basophils.

[39] This elicits degranulation of the aforementioned cells which release potent cytokines and chemokines, thus triggering inflammation and causing the symptoms characteristic of allergy.

[40] During the oral food challenge, they are administered a full age-appropriate serving of a suspected allergen in escalating size increments.

[5] A 2008 joint United Kingdom-Israel study by George Du Toit et al. observed that Jewish children in the UK have a 10-fold higher prevalence of peanut allergy compared to Jewish children of similar ancestry in Israel, where solid food introduction during infancy commonly includes a popular peanut butter-based snack.

[6][15][3] Treatment for accidental ingestion of peanut products by allergic individuals varies depending on the sensitivity of the person.

[2] Immunotherapy involves attempts to reduce allergic sensitivity by repeated exposure to small amounts of peanut products.

[52] Sublingual immunotherapy involves putting gradually increasing doses of an allergy extract under a person's tongue.

[14] A meta-analysis found that death due to overall food-induced anaphylaxis was 1.8 per million person-years in people having food allergies, with peanut as the most common allergen.

The Culinary Institute of America, a premier school for chef training, has courses in allergen-free cooking and a separate teaching kitchen.

Nevertheless, there are no labeling laws to mandatory declare the presence of trace amounts in the final product as a consequence of cross-contamination, except in Brazil.

[81][83] The European Union requires listing for those eight major allergens plus molluscs, celery, mustard, lupin, sesame and sulfites.

These products are regulated by the Food Safety and Inspection Service (FSIS), which requires that any ingredient be declared in the labeling only by its common or usual name.

This concerns labeling for ingredients present unintentionally as a consequence of cross-contact or cross-contamination at any point along the food chain (during raw material transportation, storage or handling, due to shared equipment for processing and packaging, etc.).