Hypersensitivity, Asthma, and Allergic Responses

The immune system is crucial for maintaining health and protecting the human body against microbial invasion. This same mechanism, however, can cause exaggerated immunological and inflammatory responses, resulting in severe outcomes known as hypersensitivity reactions. Type I, Type II, Type III, and Type IV hypersensitivity reactions are the four traditional classifications for hypersensitivity reactions:

• Type I hypersensitivity, commonly known as an immediate reaction, involves the generation of antibodies against the soluble antigen via immunoglobulin E (IgE). As a result, mast cells degranulate and histamine and other inflammatory mediators are released.
• Type II hypersensitivity, often known as cytotoxic reactions, involves IgG and IgM antibodies, which activate the complement system and cause cell damage or lysis.
• Type III hypersensitivity, also known as immune complex reactions, is caused by IgG, IgM, and sometimes IgA antibodies. The buildup of these immunological complexes activates the complement system, leading polymorphonuclear leukocytes (PMNs) to chemotaxis and, eventually, tissue damage.
• Type IV hypersensitivity, commonly known as delayed hypersensitivity, is characterised by T-cell-mediated reactions. As a result of cytokine release, T-cells or macrophages become activated, causing tissue damage.

Sell et al. established a more recent taxonomy that accounts for different immune system components and divides the responses into seven parts. The focus of this study, however, will be on the classic type I hypersensitivity reactions.

Atopic disorders, which are exaggerated IgE-mediated immune responses (i.e., allergic: asthma, rhinitis, conjunctivitis, and dermatitis), and allergic diseases, which are immunological responses to foreign allergens, are examples of type I hypersensitivities (i.e., anaphylaxis, urticaria, angioedema, food, and drug allergies). The allergens that cause type I hypersensitivity might be mild (e.g., pollen, mites, foods, medications, etc.) or hazardous (e.g., insect venoms). The response may emerge in many parts of the body and result in events such as:

• Nasal allergic rhinitis or hay fever 
• Ocular allergic conjunctivitis, potentially due to seasonal allergens such as pollen or mold spores 
• Dermatological hives, atopic eczema, or erythema
• Soft tissue angioedema
• Pulmonary reactions, such as allergic asthma or hypoxia
• Systemic reaction, which is a life-threatening medical emergency, and also known as anaphylaxis.

Certain risk factors increase the probability of allergic disorders. Geographical distribution, environmental risks such as pollution or socioeconomic status, genetic susceptibility, or the "hygiene hypothesis" are among these factors. According to the "cleanliness hypothesis," our contemporary society's habits of high hygiene and a lack of early exposure to numerous microorganisms or antigens may result in immune system deficiencies. As a result, the theory proposes that early exposure to a varied variety of microbes and antigens may result in lower overall incidence of allergies, asthma, and other immunological diseases.

When immune system proteins (antibodies) mistakenly identify a harmless substance, such as tree pollen, as an invader, an allergic reaction develops. Antibodies bind to antigens in an attempt to defend your body from the substance.Your immune system's chemicals produced allergy symptoms such as nasal congestion, runny nose, itchy eyes, and skin reactions. This similar response affects the lungs and airways in certain patients, resulting in asthma symptoms.

Are allergies and asthma treated differently?

Most treatments are designed to treat either asthma or allergic rhinitis. But a few treatments help with both conditions. Some examples:

• Leukotriene modifier. This drug can help with both allergic rhinitis and asthma symptoms. This daily medication, known as a leukotriene modifier, aids in the management of immune system chemicals released after an allergic reaction. Montelukast (Singulair) is a leukotriene modifier that can be used to treat asthma as well as allergic rhinitis.
• Anti-allergy injections (immunotherapy). Allergy injections can aid in the asthma treatment by gradually reducing your immune system's response to certain allergy triggers. Immunotherapy is getting little injections of the allergens that cause your symptoms on a regular basis.
• Over time, your immune system builds a tolerance to the allergens, and your allergic symptoms diminish. As a result, asthma symptoms decrease. This treatment usually requires a series of injections over time.
• IgE (anti-immunoglobulin E) therapy. When you have an allergy, your immune system misidentifies a specific chemical as hazardous and stimulate the immune system called IgE against the allergen.