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