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Deconstructing allergies: mechanisms, treatments, and prevention

Modern populations have witnessed a dramatic surge in the number of people grappling with allergies, a condition that can lead to a myriad of health issues such as eczema, asthma, hives, and, in severe cases, anaphylaxis. For those who are allergic, these substances can trigger life-threatening reactions due to their abnormal immune response. Common allergens include antibiotics like penicillin, as well as animals, insects, dust, and various foods. The need for strict dietary restrictions and the constant fear of accidental encounters with allergens often plague patients and their families. Negligent business practices and mislabelled food have even led to multiple reported deaths, underscoring the gravity of allergies and their alarming rise in prevalence.

The primary reason for the global increase in allergies is believed to be the lack of exposure to microorganisms during early childhood. The human microbiome, a collection of microorganisms that live in and on our bodies, is a key player in our immune system. The rise in sanitation practices is thought to reduce the diversity of the microbiome, potentially affecting immune function. This lack of exposure to infections may cause the immune system to overreact to normally harmless substances like allergens. Furthermore, there is speculation about the impact of vitamin D deficiency, which is becoming more common due to increased indoor time. Vitamin D is known to support a healthy immune response, and its deficiency could worsen allergic reactions.

Immune response

Allergic responses occur when specific proteins within an allergen are encountered, triggering an immune response that is typically used to fight infections. The allergen's proteins bind to complementary antigens on macrophage cells, causing these cells to engulf the foreign substance. Peptide fragments from the allergen are then presented on the cell surface via major histocompatibility complexes (MHCs), activating receptors on T helper cells. These activated T cells stimulate B cells to produce immunoglobulin E (IgE) antibodies against the allergen. This sensitizes the immune system to the allergen, making the individual hypersensitive. Upon re-exposure to the allergen, IgE antibodies bind to allergen peptides, activating receptors on mast cells and triggering the release of histamines into the bloodstream. Histamines cause vasodilation and increase vascular permeability, leading to inflammation and erythema. In milder cases, patients may experience itching, hives, and runny nose; however, in severe allergic reactions, intense swelling can cause airway constriction, potentially leading to respiratory compromise or even cessation. At this critical point, conventional antihistamine therapy may not be enough, necessitating the immediate use of an EpiPen to alleviate symptoms and prevent further deterioration.

EpiPens administer a dose of epinephrine, also known as adrenaline, directly into the bloodstream when an individual experiences anaphylactic shock. Anaphylactic shock is typically characterised by breathing difficulties. The primary function of the EpiPen is to relax the muscles in the airway, facilitating easier breathing. Additionally, they counteract the decrease in blood pressure associated with anaphylaxis by narrowing the blood vessels, which helps prevent symptoms such as weakness or fainting. EpiPens are the primary treatment for severe allergic reactions leading to anaphylaxis and have been proven effective. However, the reliance on EpiPens underscores the necessity for additional preventative measures for individuals with allergies before a reaction occurs.

Preventative treatment

Young individuals may have a genetic predisposition to developing allergies, a condition referred to as atopy. Many atopic individuals develop multiple hypersensitivities during childhood, but some may outgrow these allergies by adulthood. However, for high-risk atopic children, preventive measures may offer a promising solution to reduce the risk of developing severe allergies.

Clinical trials conducted on atopic infants explored the concept of immunotherapy treatments, involving continuous exposure to small doses of peanut allergens to prevent the onset of a full-blown allergy. Initially, skin prick tests for peanut allergens were performed, and only children exhibiting negative or mild reactions were selected for the trial. Those with severe reactions were excluded due to the high risk of anaphylactic shock with continued exposure. The remaining participants were randomly assigned to either consume peanuts or follow a peanut-free diet. Monitoring these infants as they aged revealed that continuous exposure to peanuts reduced the prevalence of peanut allergies by the age of 5. Specifically, only 3% of atopic children exposed to peanuts developed an allergy compared to 17% of those in the peanut-free group.

The rise in severe allergies poses a growing concern for global health. Once an atopic individual develops an allergy, mitigating their hypersensitivity can be challenging. Current approaches often involve waiting for children to outgrow their allergies, overlooking the ongoing challenges faced by adults who remain highly sensitive to allergens. Implementing preventive measures, such as early exposure through immunotherapy, could enhance the quality of life for future generations and prevent sudden deaths in at-risk individuals.

In conclusion, a dramatic surge in the prevalence of allergies in modern populations requires more attention from researchers and health care providers. Living with allergies can bring many complexities into someone’s life even before they potentially have a serious reaction. Currently treatments are focused on post-reaction emergency care, however preventative strategies are still a pressing need. With cases of allergies predicted to rise further, research into this global health issue will become increasingly important. There are already promising results from early trials of immunotherapy treatments, and with further research and implementation these treatments could improve the quality of life of future generations. 

Written by Charlotte Jones

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