Peanut allergy


The prevalence among children in the US and other industrialized countries is on the rise.

Affects approximately 1-2% of children.

Symptoms of an allergic reaction: vomiting, diarrhea, indigestion, stomach cramps, wheezing, breathing difficulties, dizziness, confusion, indigestion, continuous coughing, tightening of the throat, voice hoarseness, weakened pulse, paleness or blue coloring of the skin, hives, swelling that may include the lips or tongue, dizziness, and confusion.

Peanut allergy affects approximately 1 million children in the U.S. and only 1 out of 5 of these children will outgrow their allergy.

It usually persists into adulthood.

It is occasionally life-threatening, and accounts for the majority of deaths related to food allergy.

No approved treatment.

Exposure to peanuts  can occur by: direct contact, cross-contamination or inhalation.

The standard of care is strict elimination of consumption and timely administration of rescue medications in case of an allergic reaction or accidental exposure.

The rapid administration of epinephrine on presentation of allergic symptoms is standard care.

A common cause of emergency department visits for food induced anaphylaxis and has been associated with fatal reactions.

Accidental exposures may cause reactions, even with small amounts of allergen, leading to a lifetime risk of severe reactions.

Several risk factors:  young children are at increased risk as compared to an older individual with a more mature digestive system, history of previous allergy to peanuts, susceptibility to other allergies, family history of food allergies and atopic dermatitis

A type of food allergy to peanuts, that is different from tree nut allergies.

They are part of the plant legume family.


Although development of a peanut allergy usually lasts a lifetime, studies have shown that 20% of children outgrow their allergy.

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

Anaphylaxis may occur, and the principal treatment for anaphylaxis is epinephrine as an injection.

Frequency is 0.6% of the population.

Infants with severe eczema or egg allergy should undergo peanut specific IgE measurement, skin prick testing, or both prior to introduction of peanuts at ages 4-6 months.

In Western countries, the incidence of peanut allergy is between 1-3%.

There has been a sudden increase in number of cases recently.

It is due to a type I hypersensitivity reaction of the immune system.

A common cause of food-related fatal and near-fatal allergic reactions.

It is one of the most common causes of food-related deaths.

A meta-analysis found that death due to overall food-induced anaphylaxis was 1.8 per million person-years in people having food allergies.

In the above analysis, peanut as the most common allergen.

It is one of the most severe food allergies due to its prevalence, persistency, and potential severity of allergic reaction.

Peanut allergy is one of the least likely food allergies to be outgrown.

Prevention may be partly achieved through early introduction of peanuts to the diets of pregnant women and babies.

Symptoms of peanut allergy are related to the action of Immunoglobulin E (IgE) and other anaphylatoxins which act to release histamine and other mediator substances from mast cells

Histamine induces vasodilation of arterioles and constriction bronchospasm.

Patients with confirmed peanut allergy may have cross-reactivity to tree nut, soy, and other legumes, such as peas and lentils.

Peanut allergy is associated with several specific proteins categorized according to four common food allergy superfamilies: Cupin, Prolamin, Profilim, and Bet v-1-related proteins.

The major allergens which means that they trigger an immunological response in more than 50% of the allergic population.

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

Some of the peanut allergens can undergo enzymatic and non-enzymatic modifications which makes them more likely to bind to ligands on antigen-presenting cells.

Uncommon in children of undeveloped countries where peanut products have been used to relieve malnutrition.

It is suggested exposure to diverse food sources early in life, increases immune capability, whereas food selection by children in developed countries is more limited, reducing immune capability.

In children with higher allergy risk due to their parents with peanut allergy, the consumption of peanut proteins while 4 to 11 months old, the risk of developing peanut allergy before the age of 5 years decreases by 11-25%.

Introducing foods containing peanuts to infants at high risk of developing peanut allergy is safe and that there is an 81% relative reduction in the subsequent development of a peanut allergy (LEAP study).



It is recommendsed  that infants at high risk of developing peanut allergy due to having severe eczema, egg allergy, or both should be introduced to peanut in their diets as early as 4-6 months to reduce the risk of peanut allergy. 

Insufficient evidence exists to determine whether maternal peanut exposure, or early consumption of peanuts by children, affects sensitivity for peanut allergy.

Peanut allergies are much more common in infants with oozing and crusted skin rashes.

Sensitive children may react via ingestion, inhalation, or skin contact to peanut allergens.

Airborne particles in industry exposed environments or from cooking, can produce respiratory effects in sensitive patients..

Dendritic cells recognize peanut allergens as foreign pathogens, and causes the allergic response.

Dendritic cells present the antigens on MHC class II receptors and these antigens are recognized by cell receptors on T cells.

The contact along with the release of the cytokine IL-4 induces their differentiation into CD4+ Th2 cells.

The Th2 cells proliferate and release pro-inflammatory cytokines such as IL-4, IL-5 and IL-13 which can be bound to receptors on B cells of the IgM subtype.

The Receptor-cytokine binding causes their differentiation into IgE which can then be bound onto mast cells, eosinophils and basophils.

Degranulation of the mast cells, eosinophils and basophils which release potent cytokines and chemokines, thus triggering an inflammation and causing the symptoms characteristic of allergy.

Diagnosis of food allergies, including peanut allergy, begins with a medical history and physical examination, but multiple studies demonstrate 50% to 90% of presumed food allergies are not.

Diagnosis of peanut allergy: detailed history of the person, skin prick testing, a blood test that measures the amount IgE antibodies in the blood, and an oral food challenge. 

Skin prick tests can be used to confirm specific food allergies and can identify specific IgE bound to cutaneous mast cells.

A glycerinated allergen extract drop is placed on the patient’s skin, and it is then pricked through the drop.

This skin prick test procedure is repeated with two controls: a histamine drop designed to elicit an allergic response, and a saline drop designed to elicit no allergic response.

A positive peanut allergic test is one in which the extract wheal is 3mm larger than the saline wheal.

A skin prick test is monitored to identify whether a reaction or a bump develops on the skin, usually within 30 minutes.

A positive skin prick test is about 50% accurate, so a positive skin prick test alone is not diagnostic of food allergies.

The diagnostic test of a double-blind placebo-controlled oral food challenge with age-appropriate serving of a suspected allergen in escalating size increments is a standard testing procedure,

Individuals are administered a full age-appropriate serving of a suspected allergen in escalating size increments.

Such oral food challenges pose risks, with 1 study showing 48% of challenges resulted in allergic reactions, with 28% of these resulting in severe reactions.

In open food challenge studies patients are fed an age-appropriate serving of a suspected food allergen in its natural form. and observed for objective symptoms resulting from ingestion of the food, such as vomiting or wheezing.

The development of symptoms is considered diagnostic of food allergy if the symptoms correlate with findings from the patient’s medical history and laboratory testing such as the skin prick test.

An oral food challenge is administered as a small amount of peanut to the individual and then monitored for a reaction: The amount of allergen is increased  until a reaction is observed. 

By feeding babies foods that contain peanuts when they are as young as four to six months of age peanut allergy may be prevented.

Two population studies from Australia found that the introduction of peanuts in early infancy was associated with a lower risk of peanut allergy than introduction at 12 months or later: The early introduction of peanuts was not associated with a statistically significant change in the prevalence of peanut allergy across the population.

Infants with mild to moderate eczema should have peanut-containing foods introduced into their diets at around 6 months to reduce the risk of peanut allergy. 


It is  recommended that other solid foods should be started in infants before introducing peanut-containing foods.


The SLIT study found that two-thirds of children who had a peanut allergy and received daily doses of dissolved peanut protein administered under the tongue were able after several years of treatment to tolerate eating about 2.5 peanut kernels. 

Presently, there is no cure.

Strict avoidance of peanuts and peanut-containing foods is imperative.

It tends to resolve in childhood less often than allergies to soy, milk, egg, and wheat.

Annual re-evaluation of peanut allergy is recommended on a yearly basis for young children, and every few years or longer for older children and adults.

In high-risk influence the early introduction of peanut protein reduces the development of peanut allergy by about 80%.

In the United States, the Food Allergen Labeling and Consumer Protection Act of 2004 (FALCPA) requires companies to disclose on the label whether a packaged food product contains any of these eight major food allergens, added intentionally: cow’s milk, peanuts, eggs, shellfish, fish, tree nuts, soy and wheat.

Oral immunotherapy can induce desensitization, which is a transient upward shift in threshold reactivity to an allergen with controlled exposer to the same allergen.

Epicutaneous immunotherapy uses skin patches containing peanut protein to desensitize patients.

Palforzia approved for peanut allergy therapy.

Oral  immunotherapeutic agent Palforzia is indicated for the mitigation of allergic reactions, including anaphylaxis that may occur due to accidental peanut exposure in patients aged 4-17 years who have a confirmed peanut allergy diagnosis.


Oral  immunotherapy is indicated for use in conjunction with a peanut-avoidant diet.

Palforzia is composed of a  powder made from peanuts. Peanut allergen powder is the only food allergy immunotherapy presently approved and is used for peanut allergy.

Palforzia is taken in small amounts daily and gradually increased, resulting  in a less severe allergic reaction to peanuts over time.

It can cause anaphylaxis at any time during therapy and is only available through a restricted program under a Risk Evaluation and Mitigation Strategy (REMS).

In a trial involving children, 1 to 3 years of age with peanut allergies, epi-cutaneous immunotherapy for 12 months with superior to placebo in desensitize in children to peanuts an increase in the peanut does that triggered allergic symptoms.

A peanut patch worn by children allergic to peanuts, cause desensitization in 67% of participants.


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