What occurs in the cell during an allergic reaction?

Seasonal allergy (disorder),Allergy to substance (disorder),Pseudoallergy to substance (disorder),House dust mite allergy (disorder),Drug pseudoallergy (disorder), Drug allergy,Drug allergy (disorder), Medicine allergy, Allergy to drug, Medication allergy,Allergy to caffeine (disorder),Gastrointestinal food allergy (disorder), Gastrointestinal food sensitivity,Upper respiratory tract allergy (disorder),Dialysis fluid allergy (disorder),Animal dander allergy, Dander (animal) allergy (disorder), Allergy to animal,Allergy to rubber (disorder),Allergy to wool (disorder),Food allergy (disorder),Allergy to wasp venom (disorder),Allergy to plant (disorder),Allergy to tree resin (disorder),Allergy to pollen (disorder),Oral rehydration salts allergy (disorder),Allergy to flavour, Allergy to flavor (disorder),Multiple electrolyte infusion allergy (disorder),Terpenes allergy (disorder),Metal allergy (disorder),Citrate allergy (disorder),Base allergy (disorder),Clostridium botulinum toxin allergy (disorder),Allergy to biocide (disorder),Allergy to adhesive (disorder),Allergy to animal hair (disorder),Feather allergy (disorder),Fungus allergy, Allergy to fungus (disorder),Dust allergy (disorder),airway allergy,food hypersensitivity,allergies#hypersensitivity#sensitivity#allergic reaction#anaphylaxis,

 

Exposure to the allergen that may occur through respiration or eating, leads to the elevation of immunoglobulin E (IGE), which target T lymphocytes, which then transform from native to reactive.

The latter have high affinity for mastocytes and basophiles. The binding of the antigen to 2 IGE molecules leads to the release of lipid based precursor mediators and cytokines. During activation, the mediators localized on the mastocyte are secreted to the extracellular matrix.

These granules contain histamines, heparins etc. Histamines are released to higher degrees in the morning hours of the day, reaches its peak secretion levels in midday.

The highest concentrations are observed on the skin, in the mucosa of the lungs, and the gastrointestinal mucosa. Histamines are released in tissues by mastocytes, whereas in the blood it is secreted by basophiles.

The elevation of histamines leads to:

  1. Local erythema (inflammation)
  2. Vasodilation
  3. Red skin
  4. Rash
  5. Increase of capillary permeability

The key actors of allergic hyper-sensibility:

  • The antigen (allergen)
  • IGE antibodies
  • mastocytes, basophiles
  • mediators secreted by mastocytes in the antigen-antibody conflict

The allergic reaction is caused by the allergen or the so called antigen, which in the majority of cases is a protein, or at times a carbohydrate, or even rare chemicals with low molecular weights. New allergens can be observed to be emerging in the world nowadays.

This is due to the high levels of industrialization which are heavily affecting the environment and by consequence the lifestyles of populations across the globe.  This has in turn, led to the increase of allergic condition incidence on the world population.

Allergic emergences come as a consequence of disruption of the normal functioning of the gastrointestinal tract, the skin and the respiratory tract.  

As a consequence the allergens are introduced through the air, food, and skin contact.

 

Atopic individuals

Individuals predisposed to allergic conditions are also referred to as atopic individuals (the allergen is introduced into the body from the external environment). This can be verified through scratch tests with allergens which are performed on the skin:

  • pollens
  • dust
  • domestic animals
  • fungi

 

Being atopic is an individual tendency for producing IGE antibodies, and thus to be allergic. Allergic conditions have been on the rise, for example at the beginning of the 20th century, the prevalence of allergic rhinitis was 1%, and nowadays it has risen to 15-20%.

To fully understand the condition of an allergic patient, the physician must thoroughly interrogate the latter.

  1. The physician must make the temporal-symptomatic connections.
  2. The location where symptoms occur (home, work environment, holiday etc)
  3. The activity the patient was undertaking at the emergency of the symptoms (was the patient working in the garden, cleaning etc)
  4. The climate conditions which may have triggered the symptoms (fluctuations in temperature, humidity)
  5. Is there a familial predisposition? (family history of allergies)
  6. The physician must evaluate the severity of the symptoms

Medically Reviewed by a doctor on 22 Aug 2017
Medical Author: Dr. med. Diana Hysi