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Allergy immunotherapy (AIT), which is also termed allergen desensitization or hypo-sensitization was first introduced by Leonard Noon and John Freeman in 1911. They proposed that people with hay fever were sensitive to grass pollen toxins. Desensitization is "a method, to develop a temporary state of tolerance to an agent responsible for an allergic or hypersensitivity reaction." This activity reviews the indications, contraindications, and techniques for allergy immunotherapy and highlights the role of the interprofessional team in the management of patients with allergies. Objectives: Describe the indications for allergy immunotherapy. Describe how allergy immunotherapy is done. Outline the importance of collaboration and coordination within the interprofessional team in optimizing the care of patients requiring allergy immunotherapy. Discuss future trends in allergy immunotherapy Access free multiple choice questions on this topic.

Allergy immunotherapy (AIT),  also referred to as allergen desensitization or hypo-sensitization was first introduced by Leonard Noon and John Freeman in 1911, they proposed that people with hay fever were sensitive to grass pollen toxins. [1]Noon is credited for developing a process involved in the extraction of timothy pollen in distilled water and then boiling it to create an extract. [1] This extract was then injected in increasing doses to alleviate symptoms in patients.  This concept is widely in use today with a modified approach. Currently, the term immunotherapy is used to describe all methods to overcome abnormal immune responses with induction of clonal deletion, anergy, immune tolerance, and immune deviation. [2]However, the term desensitization is "a method, to develop a temporary state of tolerance to an agent responsible for an allergic or hypersensitivity reaction." [3]Furthermore, immunotherapy is a disease-modifying treatment and the effects can last longer even after stopping the treatment, which then provides prophylactic effects.[3][4][5][6][7][8]

Giving allergy immunotherapy should be given with tremendous care since it involves administering an agent that a patient is already known to be allergic to. Complications due to immunotherapy include systemic reactions such as anaphylaxis, large cutaneous reactions, and a local reaction at the injection site. [2] Although rare, even fatal reactions to subcutaneous allergy immunotherapy can occur.  One of the greatest risk factors for such reactions is asthma, especially uncontrolled or unstable asthma.[16][17]   Another risk factor is an accidental intramuscular injection which can cause an increased risk of systemic reaction due to rapid absorption. Sublingual administration has only shown severe reactions associated with the first dose and subsequent doses cause less severe symptoms of the oral mucosa, throat, or gastrointestinal tract. [18][19]  Due to these complications, patients must be aware of the risk vs benefits associated with immunotherapy. Thus, immunotherapy should be given under the guidance of a specialist trained in the field and informed consent should be gathered. Management of Complications  [2] Topical corticosteroids, antihistamines, or cool compresses for local reaction Epinephrine is the mainstay treatment for anaphylaxis. The physician should re-visit the benefit versus risk of continuing immunotherapy after systemic reactions.[2]

Current and Future Trends in Allergen Immunotherapy Recent advances in understanding the mechanism and the long-term effects of immunotherapy are encouraging for future therapies. There are also new approaches being used to improve safety and overcoming the risk of severe adverse allergic reactions during immunotherapy. Newer allergen preparations available include allergoids, recombinant allergens (recA), and modified-recombinant allergens (recA). Studies on virus-like particles and CpG-motifs, adjuvants like MPL, and aluminum hydroxide have been shown to increase immunological response and can improve safety and efficacy.[8]  Other newer approaches to allergen immunotherapy include the application of extract patches on the skin and/or inguinal lymph node injection. Furthermore, recombinant technology or chemicals may alter allergen molecules that make them less reactive; this may be due to suppression of Th2 responses or stimulation of toll-like receptors (approval is pending).[28] The new advances in allergy immunotherapy not only provide disease-modifying treatments but are also cost-effective and improve the quality of life.[29] Yet, with the historical efficacy and safety of immunotherapy, it remains underutilized. Safety, Doses, Delivery, and Application of Immunotherapy Comparison of pediatric and adult systemic reactions to subcutaneous immunotherapy shows significant Grade 1 and Grade 2 systemic reactions that are higher in a pediatric population than adults. However, further studies are needed to evaluate the dosing strategy in children.[30] Subcutaneous allergen immunotherapy has shown that SCIT rarely causes any major clinical problems; there is a risk of less than 1.5% in patients who are HIV positive without AIDS, cancer (in remission), severe asthma, transplantation,  and during pregnancy, based on web-based survey.[31] Food immunotherapy has exploded due to numerous studies suggestive of its benefit.  One such study was the LEAP (Learning Early About Peanut Allergy) that showed that high-risk infants with atopic dermatitis and egg allergy were able to build a tolerance to the ingestion of peanut if given early.[32] Studies investigating oral immunotherapy with other foods and various delivery methods are currently being done.

Food immunotherapy has exploded due to numerous studies suggestive of its benefit.  One such study was the LEAP (Learning Early About Peanut Allergy) that showed that high-risk infants with atopic dermatitis and egg allergy were able to build a tolerance to the ingestion of peanut if given early.[32] Studies investigating oral immunotherapy with other foods and various delivery methods are currently being done. Future trends in allergy immunotherapy support the concept of precision medicine. It should always be individualized and specific for a particular patient. Although it has been shown to prevent the development of asthma and new sensitization, this has only been shown in children. On the other hand, adults should be evaluated differently, and it should be used for the primary objective of bringing relief to their allergic symptoms. Further research is needed to address research gaps in allergy immunotherapy.  Such gaps include which sensitivities should be targeted to prevent disease, timing of immunotherapy, length of treatment, monoallergen vs polyallergen treatment, etc. However, the future is exciting, and with the increasing understanding of the immune system, the age of precision medicine has arrived.