Differential diagnosis
Before a diagnosis of allergic disease can be confirmed, other possible causes of the presenting symptoms should be considered.[91] Vasomotor rhinitis, for example, is one of many illnesses that share symptoms with allergic rhinitis, underscoring the need for professional differential diagnosis.[92] Once a diagnosis of asthma, rhinitis, anaphylaxis, or other allergic disease has been made, there are several methods for discovering the causative agent of that allergy.
Prevention
Further information: Allergy prevention in children
Giving peanut products early may decrease the risk allergies while only breastfeeding during at least the first few months of life may decrease the risk of dermatitis.[93][94] There is no good evidence that a mother's diet during pregnancy or breastfeeding affects the risk.[93] Nor is there evidence that delayed introduction of certain foods is useful.[93] Early exposure to potential allergens may actually be protective.[6]
Fish oil supplementation during pregnancy is associated with a lower risk.[94] Probiotic supplements during pregnancy or infancy may help to prevent atopic dermatitis.[95][96]
Management
Management of allergies typically involves avoiding what triggers the allergy and medications to improve the symptoms.[7] Allergen immunotherapy may be useful for some types of allergies.[7]
Medication
Several medications may be used to block the action of allergic mediators, or to prevent activation of cells and degranulation processes. These include antihistamines, glucocorticoids, epinephrine (adrenaline), mast cell stabilizers, and antileukotriene agents are common treatments of allergic diseases.[97] Anti-cholinergics, decongestants, and other compounds thought to impair eosinophil chemotaxis, are also commonly used. Although rare, the severity of anaphylaxis often requires epinephrine injection, and where medical care is unavailable, a device known as an epinephrine autoinjector may be used.[27]
Immunotherapy
Main article: Allergen immunotherapy
Anti-allergy immunotherapy
Allergen immunotherapy is useful for environmental allergies, allergies to insect bites, and asthma.[7][98] Its benefit for food allergies is unclear and thus not recommended.[7] Immunotherapy involves exposing people to larger and larger amounts of allergen in an effort to change the immune system's response.[7]
Meta-analyses have found that injections of allergens under the skin is effective in the treatment in allergic rhinitis in children[99][100] and in asthma.[98] The benefits may last for years after treatment is stopped.[101] It is generally safe and effective for allergic rhinitis and conjunctivitis, allergic forms of asthma, and stinging insects.[102]
The evidence also supports the use of sublingual immunotherapy for rhinitis and asthma but it is less strong.[101] For seasonal allergies the benefit is small.[103] In this form the allergen is given under the tongue and people often prefer it to injections.[101] Immunotherapy is not recommended as a stand-alone treatment for asthma.[101]
Alternative medicine
An experimental treatment, enzyme potentiated desensitization (EPD), has been tried for decades but is not generally accepted as effective.[104] EPD uses dilutions of allergen and an enzyme, beta-glucuronidase, to which T-regulatory lymphocytes are supposed to respond by favoring desensitization, or down-regulation, rather than sensitization. EPD has also been tried for the treatment of autoimmune diseases but evidence does not show effectiveness.[104]
A review found no effectiveness of homeopathic treatments and no difference compared with placebo. The authors concluded that, based on rigorous clinical trials of all types of homeopathy for childhood and adolescence ailments, there is no convincing evidence that supports the use of homeopathic treatments.[105]
According to the National Center for Complementary and Integrative Health, U.S, the evidence is relatively strong that saline nasal irrigation and butterbur are effective, when compared to other alternative medicine treatments, for which the scientific evidence is weak, negative, or nonexistent, such as honey, acupuncture, omega 3's, probiotics, astragalus, capsaicin, grape seed extract, Pycnogenol, quercetin, spirulina, stinging nettle, tinospora or guduchi. [106][107]
Epidemiology
The allergic diseases—hay fever and asthma—have increased in the Western world over the past 2–3 decades.[108] Increases in allergic asthma and other atopic disorders in industrialized nations, it is estimated, began in the 1960s and 1970s, with further increases occurring during the 1980s and 1990s,[109] although some suggest that a steady rise in sensitization has been occurring since the 1920s.[110] The number of new cases per year of atopy in developing countries has, in general, remained much lower.[109]
Before a diagnosis of allergic disease can be confirmed, other possible causes of the presenting symptoms should be considered.[91] Vasomotor rhinitis, for example, is one of many illnesses that share symptoms with allergic rhinitis, underscoring the need for professional differential diagnosis.[92] Once a diagnosis of asthma, rhinitis, anaphylaxis, or other allergic disease has been made, there are several methods for discovering the causative agent of that allergy.
Prevention
Further information: Allergy prevention in children
Giving peanut products early may decrease the risk allergies while only breastfeeding during at least the first few months of life may decrease the risk of dermatitis.[93][94] There is no good evidence that a mother's diet during pregnancy or breastfeeding affects the risk.[93] Nor is there evidence that delayed introduction of certain foods is useful.[93] Early exposure to potential allergens may actually be protective.[6]
Fish oil supplementation during pregnancy is associated with a lower risk.[94] Probiotic supplements during pregnancy or infancy may help to prevent atopic dermatitis.[95][96]
Management
Management of allergies typically involves avoiding what triggers the allergy and medications to improve the symptoms.[7] Allergen immunotherapy may be useful for some types of allergies.[7]
Medication
Several medications may be used to block the action of allergic mediators, or to prevent activation of cells and degranulation processes. These include antihistamines, glucocorticoids, epinephrine (adrenaline), mast cell stabilizers, and antileukotriene agents are common treatments of allergic diseases.[97] Anti-cholinergics, decongestants, and other compounds thought to impair eosinophil chemotaxis, are also commonly used. Although rare, the severity of anaphylaxis often requires epinephrine injection, and where medical care is unavailable, a device known as an epinephrine autoinjector may be used.[27]
Immunotherapy
Main article: Allergen immunotherapy
Anti-allergy immunotherapy
Allergen immunotherapy is useful for environmental allergies, allergies to insect bites, and asthma.[7][98] Its benefit for food allergies is unclear and thus not recommended.[7] Immunotherapy involves exposing people to larger and larger amounts of allergen in an effort to change the immune system's response.[7]
Meta-analyses have found that injections of allergens under the skin is effective in the treatment in allergic rhinitis in children[99][100] and in asthma.[98] The benefits may last for years after treatment is stopped.[101] It is generally safe and effective for allergic rhinitis and conjunctivitis, allergic forms of asthma, and stinging insects.[102]
The evidence also supports the use of sublingual immunotherapy for rhinitis and asthma but it is less strong.[101] For seasonal allergies the benefit is small.[103] In this form the allergen is given under the tongue and people often prefer it to injections.[101] Immunotherapy is not recommended as a stand-alone treatment for asthma.[101]
Alternative medicine
An experimental treatment, enzyme potentiated desensitization (EPD), has been tried for decades but is not generally accepted as effective.[104] EPD uses dilutions of allergen and an enzyme, beta-glucuronidase, to which T-regulatory lymphocytes are supposed to respond by favoring desensitization, or down-regulation, rather than sensitization. EPD has also been tried for the treatment of autoimmune diseases but evidence does not show effectiveness.[104]
A review found no effectiveness of homeopathic treatments and no difference compared with placebo. The authors concluded that, based on rigorous clinical trials of all types of homeopathy for childhood and adolescence ailments, there is no convincing evidence that supports the use of homeopathic treatments.[105]
According to the National Center for Complementary and Integrative Health, U.S, the evidence is relatively strong that saline nasal irrigation and butterbur are effective, when compared to other alternative medicine treatments, for which the scientific evidence is weak, negative, or nonexistent, such as honey, acupuncture, omega 3's, probiotics, astragalus, capsaicin, grape seed extract, Pycnogenol, quercetin, spirulina, stinging nettle, tinospora or guduchi. [106][107]
Epidemiology
The allergic diseases—hay fever and asthma—have increased in the Western world over the past 2–3 decades.[108] Increases in allergic asthma and other atopic disorders in industrialized nations, it is estimated, began in the 1960s and 1970s, with further increases occurring during the 1980s and 1990s,[109] although some suggest that a steady rise in sensitization has been occurring since the 1920s.[110] The number of new cases per year of atopy in developing countries has, in general, remained much lower.[109]
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