Background

• Peanut allergy is a potentially severe immune response to proteins found in peanuts, a common legume. It is one of the most prevalent food allergies, particularly in Western countries, affecting both children and adults. Peanut allergies can trigger a range of symptoms, from mild skin reactions to severe & life-threatening anaphylaxis.
• The prevalence of peanut allergy is been increasing, and its onset often occurs during early childhood. The exact cause of this allergy remains unclear, but it is believed to involve combination of genetic and environmental factors.
• Management involves strict avoidance of peanuts and peanut-containing products, along with preparedness for emergency intervention in case of accidental exposure. Ongoing research aims a better understanding on mechanisms of peanut allergy and explore potential treatments, including immunotherapy, to mitigate the allergic response.

Epidemiology

• Prevalence:
• Peanut allergy prevalence varies across different regions. In Western countries, such as the United States, the United Kingdom, and Australia, peanut allergy is more prevalent than in many other parts of the world.
• Increasing Incidence:
• Over the past few decades, there has been a notable increase in the incidence of peanut allergy. The reasons for this rise are not entirely clear and may involve a combination of genetic, environmental, and lifestyle factors.
• Geographical Differences:
• The prevalence of peanut allergy is generally higher in Westernized countries compared to less developed regions. However, as globalization and dietary patterns change, peanut allergy is also becoming more recognized in other parts of the world.
• Age of Onset:
• Peanut allergy often manifests early in life, with many individuals developing symptoms during childhood. However, it can also occur in adults, and some individuals may carry the allergy from childhood into adulthood.
• Persistence into Adulthood:
• While some children may outgrow peanut allergies, a significant proportion of individuals carry this allergy into adulthood. The persistence of peanut allergy varies among individuals.
• Risk Factors:
• Certain risk factors have an increased likelihood of developing peanut allergy, including a family history of food allergies, other allergic conditions, and early introduction of peanuts to infants.
• Impact on Quality of Life:
• Peanut allergy has a considerable impact on quality of life and their families. Strict avoidance measures are often required to prevent allergic reactions.

Anatomy

Pathophysiology

• Sensitization:
• The initial exposure to peanut proteins leads to sensitization. In susceptible individuals, the immune system recognizes certain peanut proteins, particularly Ara h 1, Ara h 2, and Ara h 3, as foreign invaders.
• Production of IgE Antibodies:
• The immune system responds by producing specific immunoglobulin E (IgE) antibodies against these peanut proteins. IgE antibodies are designed to target and neutralize perceived threats, but in the case of allergies, they trigger an exaggerated immune response.
• Sensitizing Events:
• Subsequent exposure to peanuts can lead to sensitizing events where peanut proteins interact with IgE antibodies on surface of basophils and mast cells.
• Release of Mediators:
• Upon re-exposure, the peanut proteins cross-link with IgE antibodies on surface of the mast cells and basophils, leading to histamine release.
• Symptoms:
• Histamine and other mediators cause a range of allergic symptoms, varying from mild to severe. Symptoms may include skin reactions (hives, itching), gastrointestinal symptoms (nausea, abdominal pain), respiratory symptoms (wheezing, shortness of breath), and, in severe cases, anaphylaxis.
• Anaphylaxis:
• It is a severe & potentially life-threatening allergic reaction that can involve a combination of symptoms affecting multiple organ systems. It requires immediate medical attention and may include respiratory and cardiovascular symptoms, such as difficulty breathing and loss of consciousness.

Etiology

• Genetic Predisposition:
• There is a strong genetic component to peanut allergy. Individuals with a family history of allergies, including food allergies, asthma, or allergic rhinitis, may have a higher risk of developing peanut allergy. Specific genetic factors involved in the regulation of the immune response are thought to play a role.
• Environmental Factors:
• Early exposure to peanuts and other allergenic foods during infancy may influence the development of peanut allergy. The timing, dose, and route of exposure are crucial. Some studies suggest that delayed introduction of peanuts into the diet during infancy may increase the risk of developing peanut allergy, while early and regular exposure may have a protective effect. However, these recommendations are subject to change as research in this area evolves.
• Immune System Sensitization:
• Peanut allergy often begins with sensitization, where the immune system identifies peanut proteins as foreign invaders. This sensitization process involves the production of specific immunoglobulin E (IgE) antibodies against peanut proteins.
• Environmental Allergen Exposure:
• Exposure to allergens, such as pollen, may also contribute to the development of peanut allergy. This phenomenon, known as cross-reactivity, occurs when the immune system recognizes similar proteins in both environmental allergens and peanuts, leading to an allergic response.
• Changes in Gut Microbiota:
• The composition of gut microbiota (microorganisms in the digestive tract) during infancy and early childhood may influence the development of allergies, including peanut allergy. Disruptions in the balance of gut bacteria, influenced by factors like antibiotic use or diet, may play a role in allergic sensitization.
• Skin Exposure:
• Skin exposure to peanut proteins, especially through damaged skin, may contribute to sensitization. This is why avoiding direct contact with peanuts and peanut-containing products is emphasized, particularly in individuals with a known peanut allergy.

Genetics

Prognostic Factors

• Severity of Initial Reaction:
• The severity of the first allergic reaction to peanuts can be indicative of the potential for future reactions. Individuals who experience severe reactions, such as anaphylaxis, are often considered at higher risk for subsequent severe reactions.
• Age of Onset:
• Peanut allergies that develop in early childhood may persist into adulthood. Children who develop peanut allergies at a young age may be more likely to carry the allergy into adolescence and adulthood.
• Other Allergies and Atopic Conditions:
• Individuals with peanut allergy often have other allergic conditions, such as asthma, eczema, or allergies to other foods. The presence of multiple allergic conditions may impact the overall prognosis and management of peanut allergy.
• Family History of Allergies:
• A family history of allergies, including peanut allergy or other allergic conditions, may be a prognostic factor. Genetic predisposition can influence the likelihood and severity of peanut allergy.
• Resolution over Time:
• Some children may outgrow peanut allergies. The likelihood of resolution over time varies among individuals, and regular follow-up with an allergist can help monitor changes in peanut allergy status.
• Treatment Adherence:
• Adherence to avoidance measures and prescribed treatment plans, such as carrying an epinephrine auto-injector and following dietary restrictions, can influence the prognosis. Strict adherence to avoidance measures is crucial for preventing accidental exposures and severe reactions.
• Immunotherapy:
• Immunotherapy, such as oral immunotherapy (OIT) or sublingual immunotherapy (SLIT), may be considered for some individuals with peanut allergy. The success of immunotherapy and its impact on the long-term prognosis are areas of ongoing research.

Clinical History

• Age of Onset:
• Peanut allergies often manifest in early childhood, with many cases becoming apparent during the first exposure to peanuts or peanut-containing products. However, peanut allergies can also develop later in life.

Physical Examination

• Skin Examination:
• Eczema or Dermatitis: Individuals with peanut allergy, especially children, may have atopic dermatitis (eczema), which is a common skin condition associated with allergic conditions.
• Respiratory Examination:
• Wheezing: Wheezing or other respiratory symptoms may be indicative of allergic reactions affecting the respiratory system.
• Gastrointestinal Examination:
• Abdominal Pain: Individuals experiencing an allergic reaction may complain of abdominal pain or discomfort.
• Neurological Examination:
• Altered Mental Status: Severe allergic reactions, especially anaphylaxis, can lead to changes in mental status, including confusion or loss of consciousness.
• Oropharyngeal Examination:
• Swelling of the Lips, Tongue, or Throat: Allergic reactions can cause swelling in the oropharyngeal area, leading to difficulty breathing or swallowing.
• General Appearance:
• Pallor or Cyanosis: Pallor (paleness) or cyanosis (bluish discoloration) may be observed in severe reactions, indicating compromised oxygenation.

Age group

Associated comorbidity

• Individuals with peanut allergy may have comorbidities, often related to atopy (a genetic predisposition to develop allergic conditions).
• Common comorbidities include:
• Other Food Allergies: Allergies to tree nuts, eggs, milk, or other foods.
• Asthma: Individuals with peanut allergy may also have asthma, a respiratory condition characterized by airway inflammation.
• Atopic Dermatitis: A chronic skin condition that often coexists with allergic conditions.
• Allergic Rhinitis: Inflammation of the nasal passages due to allergies.

Associated activity

Acuity of presentation

• The initial allergic reaction to peanuts can range from mild to severe, including life-threatening anaphylaxis.
• Acute symptoms typically occur shortly after exposure and may involve:
• Skin Reactions: Hives, redness, itching, or eczema.
• Gastrointestinal Symptoms: Nausea, vomiting, abdominal pain, or diarrhea.
• Respiratory Symptoms: Sneezing, coughing, wheezing, or shortness of breath.
• Cardiovascular Symptoms: Rapid heart rate, low blood pressure, or loss of consciousness.

Differential Diagnoses

• Tree Nut Allergies:
• Individuals with peanut allergies may also be allergic to tree nuts (e.g., almonds, walnuts, cashews). Cross-reactivity between peanuts and tree nuts is common, and thorough testing is necessary to identify additional allergens.
• Other Food Allergies:
• Allergies to other foods, such as milk, eggs, soy, or shellfish, may present similar allergic reactions. Comprehensive allergy testing is essential to identify specific allergens.
• Oral Allergy Syndrome (OAS):
• OAS can cause allergic symptoms in the mouth and throat in response to the proteins found in certain fruits, vegetables, and nuts. It is associated with pollen allergies, and symptoms are usually limited to the oral cavity.
• Food Intolerance:
• Non-allergic reactions to certain foods, such as lactose intolerance or sensitivity to food additives, may cause gastrointestinal symptoms but are not mediated by the immune system.
• Eczema or Atopic Dermatitis:
• Skin conditions like eczema can cause redness, itching, and skin inflammation, often seen in individuals with atopic predispositions, including those with food allergies.
• Gastrointestinal Disorders:
• Conditions such as gastroesophageal reflux disease or irritable bowel syndrome may present with abdominal pain, nausea, or other gastrointestinal symptoms but are not allergic in nature.
• Anxiety or Panic Attacks:
• Emotional factors, including anxiety or panic attacks, may present with symptoms that mimic allergic reactions, such as difficulty breathing or chest tightness.

Laboratory Studies

Imaging Studies

Procedures

Histologic Findings

Staging

Treatment Paradigm

• Allergen Avoidance:
• Strict Dietary Avoidance: Individuals with peanut allergies must eliminate peanuts and peanut-containing products from their diet. This includes carefully reading food labels, asking about ingredients in restaurants, and being cautious about cross-contamination.
• Education and Allergen Awareness: Patient education is crucial to raise awareness about hidden sources of peanuts and to prevent accidental exposures.
• Emergency Preparedness:
• Prescription of Epinephrine Auto-Injector: Individuals with peanut allergy, especially those at risk of severe reactions, are typically prescribed an epinephrine auto-injector (such as EpiPen). This is the first-line treatment for anaphylaxis and should be carried out at all times.
• Anaphylaxis Action Plan: Developing and regularly reviewing an anaphylaxis action plan with an allergist is essential. This plan provides step-by-step instructions on how to recognize and respond to an allergic reaction, including when to use the epinephrine auto-injector.
• Immunotherapy:
• Oral Immunotherapy (OIT): OIT involves gradually exposing individuals to increasing amounts of peanut protein under medical supervision to desensitize them to peanuts. OIT is a developing area of research and may be considered for certain patients under the guidance of an allergist.
• Sublingual Immunotherapy (SLIT): SLIT is another form of immunotherapy that involves placing a small amount of peanut extract under the tongue to induce desensitization.

by Stage

by Modality

Chemotherapy

Radiation Therapy

Surgical Interventions

Hormone Therapy

Immunotherapy

Hyperthermia

Photodynamic Therapy

Stem Cell Transplant

Targeted Therapy

Palliative Care

non-pharmacological-treatment-of-appendicitis

• Lifestyle modifications:
• Strict Allergen Avoidance:
• Read Food Labels: Individuals with peanut allergy should carefully read ingredient labels on all packaged foods to identify and avoid products containing peanuts or peanut-derived ingredients.
• Communicate Dietary Restrictions: Inform restaurants, food service establishments, and others about the allergy, and inquire about food preparation practices to avoid cross-contamination.
• Educate Others: Raise awareness among family members, friends, caregivers, teachers, and colleagues about the severity of the allergy and the importance of avoiding peanuts.
• Create a Safe Home Environment:
• Peanut-Free Zones: Designate certain areas in the home as peanut-free zones, especially if there are young children with peanut allergies.
• Avoid Cross-Contamination: Implement measures to prevent cross-contamination in the kitchen, such as using separate cutting boards, utensils, and cooking equipment for peanut-free meals.
• Emergency Preparedness:
• Carry an Epinephrine Auto-Injector: Individuals with peanut allergy, or their caregivers, should carry an epinephrine auto-injector at all times. Ensure that it is readily accessible and not expired.
• Anaphylaxis Action Plan: Develop and regularly review an anaphylaxis action plan with an allergist, outlining steps to take in case of accidental exposure and when to use the epinephrine auto-injector.
• Educational Initiatives:
• Allergy Education: Stay informed about the latest information on peanut allergy, treatment options, and emerging therapies. Attend educational sessions and workshops provided by allergists or support groups.
• School and Work Communication: Communicate effectively with schools and workplaces to ensure they are aware of the allergy and have appropriate protocols in place.
• Social and Recreational Activities:
• Inform Social Circles: Make sure friends, classmates, and social contacts are aware of the peanut allergy, and encourage open communication about food-related activities.
• Participate in Allergy-Friendly Events: Attend events that cater to individuals with food allergies, providing a safer environment for socializing.

Use of Epinephrine in the treatment of Peanut Allergy

• Epinephrine is a critical and potentially life-saving medication used in the emergency treatment of anaphylaxis, a severe and rapid allergic reaction that can occur in response to exposure to peanuts or other allergens.
• Epinephrine works by rapidly constricting blood vessels, relaxing airway muscles, and counteracting the effects of histamine release, which are crucial actions during an allergic reaction. Epinephrine is administered promptly at the onset of severe allergic symptoms or signs of anaphylaxis, such as swelling of face or throat, difficulty breathing, a drop in blood pressure, or a combination of symptoms involving different body systems.
• Devices such as EpiPen®, AUVI-Q®, Adrenaclick®, and Symjepi® are designed for easy and quick administration of a predetermined dose of epinephrine. These auto-injectors are portable and user-friendly, allowing individuals or their caregivers to administer the medication in emergency situations. Epinephrine is typically injected into the thigh muscle. The injection should be given through clothing, if necessary, as timely administration is crucial. In some cases, a second dose of epinephrine may be necessary if symptoms persist or recur after the initial injection. This underscores the importance of seeking emergency medical attention immediately, even after administering epinephrine.

Use of Antihistamines in the treatment of Peanut Allergy

• Antihistamines are commonly used to relieve symptoms associated with allergic reactions, including those caused by peanut allergy. However, it is important to note that antihistamines are not a substitute for epinephrine in the treatment of anaphylaxis, a severe life-threatening allergic reaction. Antihistamines primarily target histamine, a chemical released during an allergic response, and can help alleviate mild to moderate allergic symptoms.
• Antihistamines acts by blocking the effects of histamine, which is released in response to allergen exposure. Histamine is responsible for various allergic symptoms, such as itching, hives, and nasal congestion. Antihistamines can provide relief from certain allergic symptoms, such as itching, hives, and mild skin reactions. They are more suitable for less severe allergic reactions and are not effective in treating the cardiovascular and respiratory symptoms associated with anaphylaxis.
• Over-the-counter antihistamines include medications such as diphenhydramine (Benadryl), cetirizine (Zyrtec), loratadine (Claritin), and fexofenadine (Allegra). These medications are available in various forms, including tablets, liquid, and chewable forms. Antihistamines may be considered as an adjunct to epinephrine in the management of mild allergic symptoms. However, it is crucial to emphasize that antihistamines should never be used as a substitute for epinephrine in the treatment of anaphylaxis.

Use of Corticosteroids in the treatment of Peanut Allergy

• Corticosteroids, such as prednisone, are not typically used as a first-line treatment for peanut allergy or anaphylaxis. While corticosteroids have potent anti-inflammatory effects, they are not rapidly acting and are not considered the primary intervention during an acute allergic reaction. In the context of peanut allergy, the immediate administration of epinephrine is crucial in managing anaphylaxis, as it rapidly addresses the cardiovascular and respiratory symptoms. Corticosteroids may be considered in the follow-up care after the administration of epinephrine, as they can help manage lingering inflammation and prevent a potential late-phase reaction. However, their use should be under the guidance of a healthcare professional, and they are not a substitute for epinephrine in emergency situations. The cornerstone of peanut allergy management remains strict allergen avoidance, education on emergency response, and the timely use of epinephrine for severe reactions.

use-of-oral-immunotherapy-in-the-treatment-of-peanut-allergy

• Oral immunotherapy (OIT) is an evolving approach in the treatment of peanut allergy and other food allergies. OIT involves the controlled, gradual exposure to increasing amounts of peanut protein with the goal of desensitizing the individual to peanuts over time.
• Desensitization Process:
• OIT aims to desensitize individuals to peanuts by exposing them to small, controlled doses of peanut protein. The dose gradually increases over weeks or months under the supervision of healthcare professionals.
• Treatment Setting:
• OIT is typically administered in a medical setting, such as an allergist’s office or an allergy clinic, where healthcare providers can closely monitor the individual for any adverse reactions.
• Dose Escalation Phases:
• The process involves several phases of dose escalation, starting with a tiny amount of peanut protein and gradually increasing it. This continues until a maintenance dose is reached, which the individual consumes regularly.
• Regular Monitoring:
• Throughout OIT, individuals are regularly monitored for any allergic reactions. This monitoring includes clinical assessments, laboratory tests, and, in some cases, oral food challenges.
• Long-Term Maintenance:
• Once the maintenance dose is achieved, individuals continue to consume a specific amount of peanut protein daily to maintain desensitization. This helps to prevent a reaction upon accidental exposure to peanuts.

management-of-peanut-allergy

• Acute Phase:
• Recognition of Allergic Reactions: Prompt recognition of allergic reactions is crucial. Symptoms include itching & hives, too severe, including difficulty breathing and anaphylaxis.
• Epinephrine Administration: The immediate administration of epinephrine is the primary intervention for anaphylaxis. Epinephrine helps alleviate severe symptoms and is administered through an auto-injector (e.g., EpiPen) into the thigh muscle.
• Seek Emergency Medical Attention: After administering epinephrine, it is essential to seek emergency medical attention immediately. Anaphylaxis is a medical emergency, and further evaluation and treatment are necessary to manage the aftermath of the reaction.
• Anaphylaxis Action Plan: Individuals with peanut allergy should have a personalized anaphylaxis action plan, developed with their allergist. This plan outlines specific steps to take in case of an allergic reaction, including when to use epinephrine and when to seek medical help.
• Supportive Care: In addition to epinephrine, supportive care may include antihistamines for mild symptoms like itching or hives. However, antihistamines are not a substitute for epinephrine in cases of anaphylaxis.
• Chronic Phase:
• Allergen Avoidance: Strict allergen avoidance is the cornerstone of managing peanut allergy. Individuals and their caregivers must carefully read food labels, communicate dietary restrictions, and be vigilant about cross-contamination.
• Educational Measures: Education plays a key role in managing peanut allergies. This includes educating the individual, family members, caregivers, teachers, and others in the community about the severity of allergies and the importance of allergen avoidance.
• Regular Follow-Up with Allergist: Regular follow-up appointments with an allergist are crucial for monitoring the individual’s allergy status, discussing any concerns, and receiving updates on emerging treatments or management strategies.
• Emergency Preparedness: Continued education on emergency preparedness is essential. This includes proper use of epinephrine auto-injectors, recognition of symptoms, and ensuring that devices are not expired.
• Psychosocial Support: Living with a peanut allergy can have psychological and social impacts. Support groups, counseling, and educational resources can provide emotional support and coping strategies.
• Potential Immunotherapy: For some individuals, allergists may explore immunotherapeutic approaches like oral immunotherapy (OIT) under controlled conditions. This is an evolving area of treatment and requires careful consideration and supervision.

Medication

Future Trends

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References

• Peanut Allergy – statpearls
• Peanut Allergy | Causes, Symptoms & Treatment