Allergy

Signs and Symptoms of Allergies

  • Swelling of the nasal mucosa (allergic rhinitis)
  • Runny nose
  • Sneezing
  • Allergic sinusitis
  • Redness and itching of the conjunctiva (allergic conjunctivitis)
  • Rashes, such as eczema and hives (urticaria)
  • Contact dermatitis or eczema caused by substances like latex
  • Weal and flare reaction characteristic of hives and angioedema
  • Large local reaction after insect stings
  • Skin redness greater than 10cm in size

Organs Affected by Allergies

  • Nose
  • Sinuses
  • Eyes
  • Airways
  • Ears

Causes and Risk Factors of Allergies

  • Heredity, sex, race, and age as host factors
  • Environmental factors like exposure to infectious diseases, pollution, allergen levels, and dietary changes
  • Dust mite allergy triggered by house dust mite droppings
  • Allergic reactions to foods such as milk, soy, eggs, wheat, peanuts, tree nuts, fish, and shellfish
  • Rare food allergies affecting less than 1 person per 10,000 population
  • Latex allergy prevalence in general population is less than 1%
  • Latex sensitivity reported by 0.125% of surgical patients
  • Healthcare workers have higher sensitivity (7-10%)
  • Latex-rich environments can sensitize healthcare workers
  • About 10% of people report being allergic to penicillin
  • Only 10% of those who report penicillin allergy actually have it
  • Serious allergies to penicillin occur in about 0.03%
  • Drug allergies can lead to adverse drug reactions and drug eruptions
  • Allergic responses to insects can be from stinging or biting
  • Stinging insects inject venom, while biting insects introduce anti-coagulants
  • Common stinging insects include wasps, bees, hornets, and ants
  • Mosquitoes and ticks are examples of biting insects
  • Urushiol-induced contact dermatitis caused by poison ivy, poison oak, or poison sumac
  • Approximately 25% of population has strong allergic response to urushiol
  • Some people are highly sensitive and can react to even trace amounts
  • Allergic diseases are strongly familial
  • Identical twins have same allergies about 70% of the time
  • Allergic parents are more likely to have allergic children
  • Severity of allergies in children of allergic parents is often higher
  • Allergies are related to immune system irregularity, not specific allergens
  • Allergic diseases caused by inappropriate immunological responses
  • Insufficient stimulation of TH1 arm leads to overactive TH2 arm
  • Individuals in sterile environments not exposed to enough pathogens
  • Hay fever and eczema less common in larger families
  • Immigrants to industrialized world develop more allergies over time
  • Allergic diseases more common in industrialized areas
  • Developing world has lower rates of immunological and autoimmune diseases
  • Antibiotics in first year of life linked to asthma and allergies
  • Use of antibacterial cleaning products associated with higher asthma incidence
  • Birth by Caesarean section linked to increased risk of allergies

Statistics on Allergies

  • 20% of people in the developed world affected by allergic rhinitis
  • 6% of people have at least one food allergy
  • 20% have or have had atopic dermatitis
  • 1-18% of people have asthma depending on the country
  • 0.05-2% of people experience anaphylaxis

Pathophysiology and Diagnosis of Allergies

  • Allergy development involves a type I hypersensitivity reaction
  • T lymphocytes produce interleukin-4 (IL-4) in response to an allergen
  • IL-4 stimulates B cells to produce IgE antibodies
  • IgE antibodies bind to mast cells and basophils, sensitizing them to the allergen
  • Upon re-exposure to the allergen, mast cells and basophils release inflammatory mediators, causing allergic symptoms
  • Late-phase responses can occur after the acute response
  • Other leukocytes such as neutrophils, lymphocytes, eosinophils, and macrophages migrate to the initial site of the allergic reaction
  • Cytokines from mast cells may play a role in the persistence of long-term effects
  • Late-phase responses in asthma are different from other allergic responses but still involve eosinophils and T2 cells
  • Late-phase responses typically occur 2-24 hours after the initial reaction
  • Accurate diagnosis is essential for effective management of allergic diseases
  • Allergy testing can confirm or rule out allergies
  • Skin prick tests and allergy blood tests are recommended methods for assessing the presence of allergen-specific IgE antibodies
  • Both skin prick tests and blood tests are cost-effective compared to no testing
  • Regular allergy testing provides information on patient management and can improve health and quality of life

Allergy Data Sources

Reference URL
Glossary https://www.alternix.com/blogs/glossary-of-terms/allergy
Wikipedia http://en.wikipedia.org/wiki/Allergy
Wikidata https://www.wikidata.org/wiki/Q42982
Knowledge Graph https://www.google.com/search?kgmid=/m/0fd23
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