Allergy

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Allergy is a disorder of the immune system that is often called atopy. Allergic reactions occur to environmental substances known as allergens; these reactions are acquired, predictable and rapid. Strictly, allergy is one of four forms of hypersensitivity and is called type I (or immediate) hypersensitivity. It is characterized by excessive activation of certain white blood cells called mast cells and basophils by a type of antibody, known as IgE, resulting in an extreme inflammatory response. Common allergic reactions include eczema, hives, hay fever, asthma, food allergies, and reactions to the venom of stinging insects such as wasps and bees.^[1]

Mild allergies like hay fever, are highly prevalent in the human population and cause symptoms such as allergic conjunctivitis, itchiness and runny nose. Similarly, conditions such as asthma are common, in which allergy plays a major role. In some people, severe allergies to environmental or dietary allergens, or to medication, occur that may result in life-threatening anaphylactic reactions and potentially death.

A variety of tests now exist to diagnose allergic conditions; these include testing the skin for responses to known allergens or analyzing the blood for the presence and levels of allergen-specific IgE. Treatments for allergies include allergen avoidance, use of antihistamines, steroids or other oral medications, immunotherapy to desensitize the response to allergen, and targeted therapy.

Allergy, as a concept, was first defined in the early 1900s. It has later developed into several different disease mechanisms related to disordered activation of immune system. The overall study of allergy, as a concept, drastically evolved in the 1960s with the discovery of immunoglobulin E (IgE) – Kimishige Ishizaka.

The development of allergic response occurs in two phases: acute and late-phase reaction. The body’s response varies largely on the type of phase and the advancement of chemical mediation.

Allergy causation can categorized as host or environmental factors. Biological factors are strongly familial related. Environmental factors very largely on the type of living environment. Allergies are more common in industrialized countries than in countries that are more traditional or agricultural, and there is a higher rate of allergic disease in urban populations versus rural populations.

Allergic response must be differentiated from other similar diseases such as vasomotor rhinitis. Proper diagnosis ensures that the patient receives the most appropriate course of treatment.

Allergy has the potential to influence various organ systems differently. Depending of the rate of severity, it can cause cutaneous reactions, bronchoconstriction, edema, hypotension, coma and even death.

Treatment for allergic response is primarily pharmacotherapeutic. Common methodologies include immunotherapy via desensitization or hyposensitization, enzyme potentiated desensitization.

Once allergies have developed, treating the allergies and carefully avoiding those things that cause reactions can prevent allergies in the future.

Template:WikiDoc Sources

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Marufa Marium, M.B.B.S[2]

The term “allergy” was first coined in the early 1900s. It has since evolved into a number of distinct disease mechanisms linked to immune system activation that is disordered. With the discovery of immunoglobulin E (IgE) – Kimishige Ishizaka – in the 1960s, the overall study of allergy as a concept changed dramatically.

Clemens von Pirquet, a Viennese pediatrician, coined the term “allergy” in 1906 after observing that some of his patients were hypersensitive to normally harmless substances such as dust, pollen, or certain foods. Pirquet coined the term “allergy” from the Greek words allos, which means “other,” and ergon, which means “work.”^[1] All forms of hypersensitivity were previously categorized as allergies, and they were all believed to be caused by an inappropriate immune system activation. Later, it became apparent that several different disease mechanisms were involved, all of which were linked to a disordered immune system activation. Philip Gell and Robin Coombs devised a new classification scheme in 1963 that defined four types of hypersensitivity reactions, referred to as Type I to Type IV hypersensitivity.^[2] The term “allergy” was now limited to type I hypersensitivities (also known as immediate hypersensitivity), which are characterized by rapidly developing reactions. The discovery of the antibody class labeled immunoglobulin E (IgE) in the 1960s was a significant breakthrough in understanding the mechanisms of allergy. Kimishige Ishizaka and co-workers were the first to isolate and characterize IgE.^[3]

Template:WikiDoc Sources

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Marufa Marium, M.B.B.S[2]

Allergy may be classified into four subtypes based on duration], type of allergen, Blood IgE test and Organ involvement.

Allergy may be classified according to duration], type of allergen, Blood IgE test and Organ involvement into four subtypes^[1][2][3]:

Template:WikiDoc Sources

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Marufa Marium, M.B.B.S[2]

There are two stages to the development of an allergic reaction: acute and late-phase reaction. The body’s reaction depends a lot on the phase and how far chemical mediation has progressed.

There are two stages to the pathophysiology of allergic reactions. The first is an allergic reaction that occurs shortly after being exposed to an allergen. This phase can either fade away or progress into a “late phase reaction,” which can significantly prolong the symptoms of an allergic reaction and cause tissue damage.^[1]

In the early stages of acute response:

In the late stage of acute response:

Acute inflammatory response causes systemic inflammatory reaction like vasodilation, mucous secretion, nerve stimulation and smooth muscle contraction. Rhinorrhea, itchiness, dyspnea, and anaphylaxis are all symptoms of this. The symptoms may be system-wide (classical anaphylaxis) or localized to specific body systems (asthma is localized to the respiratory system and eczema is localized to the dermis) depending on the individual, allergen, and mode of introduction.

Late phase responses are common after the chemical mediators of the acute response have subsided. This is due to the migration of other leukocytes to the initial site, such as neutrophils, lymphocytes, eosinophils, and macrophages. The reaction appears 2–24 hours after the initial reaction.^[2] Mast cell cytokines may also contribute to the persistence of long-term effects. Although late phase responses in asthma are slightly different from those seen in other allergic reactions, they are still triggered by eosinophil mediator release and are still dependent on TH2 cell activity.^[3]

Template:WikiDoc Sources

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Marufa Marium, M.B.B.S[2]

Allergy may be caused by genetic, environmental and infectious factors.

Allergy may be caused by genetic, environmental and infectious factors. Anaphylaxis is a life-threatening cause of Allergy.

Common genetic causes of allergy may include^[1][2] :

• HLA class 2 genes
• Th2 cytokine genes
• Degranulation and pro-inflammatory responses

Common environmental causes of allergy may include^[3]:

• Exposure to allergen:
  • Foods( Peanut, soy, eggs, shellfish), Drugs (Antibiotics, NSAIDS, Aspirin, Sulfur containing medications etc), Insects(honeybee, bumblebee, Hornet, fire ant etc), Contrast allergy, Latex, Exercise, vaccinations
• Environmental pollution
• Alteration of microbiota
• Agricultural etiology

Common infectious causes of allergy may include^[4][5]:

• Intestinal parasites

Less common causes of allergy include:

• PRR Genes
• Th differentiation
• Hormonal imbalance
• Emotional stress
• Chronic disease flare up
• Excessive hygiene
• Nutritional deficiencies

__

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Marufa Marium, M.B.B.S[2]

Allergy must be differentiated from other diseases that cause Dermatological (Urticaria, pruritus, flushing, Angioedema), Respiratory (Rhinorrhea,chest tightness,Wheezing, Dyspnoea, Sneezing, Shortness of breath) Mucosal (Mucosal swelling affecting nose, lips, tongue, larynx, pharynx, conjunctiva, GIT) Ocular (Periorbital edema, Conjunctival Congesion, Itching), Systemic (Hypotension). Allergy can be differentiated according to the type of allergy.

Allergy must be differentiated from other diseases that cause Dermatological (Urticaria, pruritus, flushing, Angioedema), Respiratory (Rhinorrhea,chest tightness,Wheezing, Dyspnoea, Sneezing, Shortness of breath) Mucosal (Mucosal swelling affecting nose, lips, tongue, larynx, pharynx, conjunctiva, GIT) Ocular (Periorbital edema, Conjunctival Congesion, Itching), Systemic (Hypotension). Allergy can be differentiated according to the types of allergy.

On the basis Dermatological, Respiratory, Mucosal, Ocular, Systemic Manifestations, Allergy must be differentiated according to the types of allergy.

• Food Allergy is differentiated from enzyme deficiencies like lactose intolerance, fructose intolerance and malabsorption, Celiac Disease, Toxic reactions, Irritable bowel syndrome, Tyramine or caffeine toxicity.
• Allergic Rhinitis is differentiated from Acute Infectious rhinitis, Irritant rhinitis, Acute Rhinosinusitis, Hormonal Rhinitis, Vasomotor rhinitis, Gustatory Rhinitis.
• Drug Allergy can be differentiated under 2 headings, they are IgE mediated (Carcinoid Syndrome, Mastocytosis) and Non-IgE mediated (Kawasaki disease, Acute Viral or streptococcal infection, Acute graft-versus host disease, Hereditary angioedema).
• Asthma is differentiated from several respiratory diseases for example COPD, Allergic bronchopulmonary aspergillosis, Bronchiectasis, OSA, Chrug-strauss syndrome, Anxiety, Foreign Body in respiratory tract.
• Atopic Dermatitis can be differentiated from Seborrheic dermatitis, Psoriasis, Contact dermatitis, Psoriasis, Scabies, Nutrient deficiency ( Zinc, Vitamin B3, Vitamin B6), Hyper IgE syndrome, Wiskott-Aldrich syndrome, IPEX syndrome, Brutons Agammaglobulinemia.

Template:WH Template:WS __

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Marufa Marium, M.B.B.S[2]

• The incidence of [[allergy] is approximately more than fifty million in a year in US.

• The prevalence of allergy is approximately 10.6% worldwide according to a data from 2012.^[1]

• In [year], the incidence of [disease name] is approximately [number range] per 100,000 individuals with a case-fatality rate/mortality rate of [number range]%.
• The case-fatality rate/mortality rate of [disease name] is approximately [number range].

Allergy prevalence varies with age of population and type of allergic reaction. For example, Allergic skin condition or food allergy may show propensity towards children and younger population while respiratory allergic reaction affects older population more.^[2]

• Allergy usually affects individuals of the African American race. Hispanic individuals are less likely to develop allergy.^[2]

• Female are more commonly affected by allergy than male.

• The majority of [[allergy] cases are reported in industrialized region.

Template:WH Template:WS

Template:WikiDoc Sources

Please help WikiDoc by adding content here. It’s easy! Click here to learn about editing.

Template:WikiDoc Sources

Please help WikiDoc by adding content here. It’s easy! Click here to learn about editing.

Template:WikiDoc Sources

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Please help WikiDoc by adding more content here. It’s easy! Click here to learn about editing.

• Anaphylaxis (life-threatening allergic reaction).
• Breathing problems and discomfort during the allergic reaction.
• Drowsiness and other side effects of medicines.

Most allergies can be easily treated with medication. Some children may outgrow an allergy. This is particularly true of food allergies. However, as a general rule, once a substance has triggered an allergic reaction, it continues to affect the person.

Allergy shots are most effective when used to treat those with hay fever symptoms and severe insect sting allergies. They are not used to treat food allergies because of the danger of a severe reaction. Allergy shots may require years of treatment, but they work in most cases. However, they may cause uncomfortable side effects (such as hives and rash) and dangerous outcomes (such as anaphylaxis).

Template:WikiDoc Sources