What are allergies and how common are they?

Allergies are immune-mediated hypersensitivity reactions to substances (allergens) that are normally harmless to non-sensitised individuals. The most common forms: Allergic rhinitis (hay fever): over 400 million people globally — sneezing, itchy/watery eyes, nasal congestion triggered by pollen, house dust mite, pet dander, mould. Food allergy: 220-250 million — IgE-mediated reactions to food proteins (peanut, milk, egg, shellfish, nuts). Allergic asthma: a major asthma phenotype driven by airborne allergens. Drug allergy: reported by 10-20% of patients; true confirmed allergy much less common (most "penicillin allergy" labels are not genuine IgE-mediated allergy). Anaphylaxis: 1-3% lifetime risk.

What is anaphylaxis and how is it treated?

Anaphylaxis is a severe, potentially fatal systemic allergic reaction — rapid onset involving two or more organ systems simultaneously (skin + respiratory, skin + cardiovascular, gastrointestinal + cardiovascular, etc.) or severe cardiovascular collapse alone. Most common triggers: food (peanut, tree nuts, shellfish — in children); insect venom (bees, wasps — in adults); drugs (penicillin, NSAIDs, iodine contrast); exercise; latex. Treatment: IMMEDIATELY give adrenaline (epinephrine) 0.3mg IM in the lateral thigh (EpiPen). Call 999/112. Lay flat with legs raised (if not breathless). Antihistamines and corticosteroids are NOT first-line — they do not prevent or reverse anaphylaxis and should not delay adrenaline.

How is allergic rhinitis managed?

Allergic rhinitis management (ARIA guidelines): Mild/intermittent: oral or intranasal antihistamine (loratadine, cetirizine, fexofenadine). Moderate-severe or persistent: intranasal corticosteroid spray (fluticasone, mometasone, beclomethasone) — the most effective single treatment for allergic rhinitis; can be combined with antihistamine for breakthrough. Allergen avoidance measures (HEPA filters, mattress covers for dust mite). Allergen immunotherapy (SCIT or SLIT): for those with moderate-severe disease not controlled by medications — disease-modifying, reduces asthma risk.

What are the most common food allergies and how are they managed?

Most common food allergens (top 9): peanut, tree nuts, milk, egg, fish, shellfish, wheat, soy, sesame. Management: strict allergen avoidance (detailed food label reading; eating out precautions; cross-contamination awareness); emergency adrenaline auto-injector (EpiPen) carried at all times; written emergency action plan. The biggest advance: peanut oral immunotherapy (Palforzia, FDA-approved 2020 for ages 4-17) — daily oral doses of peanut protein, gradually increasing over months, desensitise peanut-allergic children, raising the threshold dose for reaction. Does not produce permanent tolerance — must be continued.

Can allergies be cured?

Most allergies cannot be permanently cured, but allergen immunotherapy (AIT) — subcutaneous (SCIT) or sublingual (SLIT) — is the only treatment that modifies the underlying disease, not just symptoms. Benefits: reduces allergy symptoms during and after treatment; may prevent progression from rhinitis to asthma; may prevent new allergen sensitisation; lasts years after the 3-5 year course. For food allergy: oral immunotherapy (OIT) desensitises but does not produce permanent tolerance (must continue). Some children naturally outgrow milk and egg allergy; peanut and tree nut allergy tends to persist.

How does GMJ News cover allergies?

GMJ News covers WHO/WAO allergy burden, IgE-mediated mechanism, anaphylaxis emergency management (adrenaline IM only), allergic rhinitis ARIA guidelines, top 9 food allergens, peanut OIT, allergen immunotherapy, the hygiene/old friends hypothesis, and dupilumab for type 2 inflammatory disease. Allergies are among the most prevalent immune conditions — directly relevant to PHIG's NCD programme and clinical practice across Georgia.

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Allergies

GMJ News knowledge hub · last reviewed September 2026 · Georgian Medical Journal

Summary Statistics Glossary GMJ news FAQ Documents Organizations Research

Allergic diseases — encompassing allergic rhinitis (hay fever; approximately 400 million people globally), food allergy (220-250 million; peanut, milk, egg, shellfish, wheat, tree nuts), drug allergy, insect venom allergy and anaphylaxis (the life-threatening systemic IgE-mediated emergency) — represent the most prevalent immune-mediated conditions globally and are increasing in prevalence, particularly in high-income countries, in association with the “old friends” hypothesis of reduced early microbial exposure disrupting immune regulation (WHO). Immediate treatment of anaphylaxis with intramuscular adrenaline (epinephrine) 0.3-0.5mg IM in the lateral thigh is the life-saving first-line measure — antihistamines and corticosteroids are adjuncts, not primary treatment, and delays in adrenaline administration are the main cause of preventable anaphylaxis deaths.

Key messages

400M+ allergic rhinitis — most prevalent immune condition

Allergic rhinitis affects over 400 million people globally — the most prevalent chronic immune-mediated condition. Food allergy affects 220-250 million; anaphylaxis occurs at approximately 1-3 per 10,000 person-years, with rising prevalence particularly in children (WHO).

Adrenaline IM is the ONLY first-line anaphylaxis treatment

Intramuscular adrenaline (epinephrine) 0.3-0.5mg in the lateral thigh is the ONLY first-line treatment for anaphylaxis. Antihistamines and corticosteroids are adjuncts ONLY — they do not prevent or reverse anaphylaxis. Delay in adrenaline is the main cause of preventable anaphylaxis deaths.

IgE-mediated — the mechanism

Classical (type I) allergy is IgE-mediated: allergen exposure → IgE production (sensitisation) → subsequent exposure → IgE + allergen complex on mast cells/basophils → degranulation → histamine, leukotrienes, prostaglandins → immediate allergic reaction (minutes).

The allergic march

The “atopic march”: atopic dermatitis (eczema, typically first) → food allergy → allergic rhinitis → asthma — a common progression in genetically susceptible individuals. Early treatment of eczema and early introduction of allergenic foods may interrupt the march.

Allergen immunotherapy — the only disease-modifying treatment

Subcutaneous allergen immunotherapy (SCIT) and sublingual immunotherapy (SLIT — tablets or drops) are the only treatments that modify the underlying allergic disease — reducing sensitisation, preventing new allergen sensitisation and potentially preventing asthma development.

Peanut oral immunotherapy — FDA approved 2020

Palforzia (peanut OIT, FDA approved 2020 for ages 4-17) desensitises peanut-allergic children — raising the threshold dose to cause a reaction from approximately 10mg to approximately 300-600mg peanut protein, dramatically reducing the risk of severe reaction from accidental exposure.

Key statistics

400M+

people with allergic rhinitis globally (WHO)

WHO

220-250M

people with food allergy globally

WHO/WAO

1-3%

lifetime risk of anaphylaxis in general population

WHO/WAO

Rising

allergy prevalence globally, especially in HICs and rapidly urbanising settings

WHO

IM only

adrenaline route for anaphylaxis (lateral thigh — NOT subcutaneous)

WAO/EAACI

2020

year FDA approved Palforzia (peanut OIT) for children aged 4-17

FDA 2020

Allergic disease spectrum — global prevalence estimates (WHO/WAO)

Source: WHO/WAO. Allergic rhinitis dominates by number; anaphylaxis is the life-threatening extreme.

Glossary of key terms

IgE-mediated (Type I) hypersensitivity
WHO/EAACIThe classical allergy mechanism: allergen exposure → B-cell class-switching to IgE production (IL-4/IL-13 signalling) → IgE binds to high-affinity IgE receptors (FcεRI) on mast cells and basophils → re-exposure: allergen crosslinks IgE on mast cells → rapid degranulation (seconds to minutes) → histamine, leukotrienes, prostaglandins, tryptase. Immediate symptoms: urticaria, angioedema, bronchospasm, hypotension. Delayed (late-phase) response: 4-8 hours later from eosinophil recruitment.

Anaphylaxis
WAO/WHOA severe, potentially life-threatening systemic hypersensitivity reaction — rapid onset (minutes to hours) involving two or more organ systems, or cardiovascular collapse alone. Diagnosis is clinical. Cardinal features: urticaria/angioedema (present in approximately 85%); respiratory compromise (wheeze, stridor); hypotension. Treatment: adrenaline 0.3-0.5mg IM lateral thigh IMMEDIATELY; call 999/112; lay supine with legs raised (unless respiratory distress — then sitting up); IV fluids; antihistamine and hydrocortisone as adjuncts only.

Allergen immunotherapy (AIT)
EAACI/WHOThe only disease-modifying treatment for IgE-mediated allergy — inducing immune tolerance by systematically exposing the patient to increasing doses of allergen. SCIT (subcutaneous immunotherapy): injections typically monthly for 3-5 years; requires specialist clinic (anaphylaxis risk). SLIT (sublingual immunotherapy): tablets or drops daily at home; established for house dust mite (Acarizax), grass pollen (Grazax) and tree pollen allergies.

Epinephrine auto-injector (EpiPen)
FDA/EMAA pre-filled single-dose injection device containing adrenaline 0.3mg (EpiPen) or 0.15mg (EpiPen Jr) — for self-administration at the first sign of anaphylaxis. Prescribed to all patients with a history of anaphylaxis or high-risk allergy (peanut, tree nut, insect venom). Must be carried at all times. Administered to the lateral thigh (can be given through clothing). Two auto-injectors should be carried — dose may need to be repeated.

Food allergens — top 9
FDA/EFSAThe nine most common food allergens (responsible for approximately 90% of food allergies in HICs): peanut; tree nuts; milk; egg; fish; shellfish/crustaceans; wheat; soy; sesame (added to FDA list 2023). EU lists 14 mandatory allergens additionally including mustard, celery, lupin, molluscs, sulphites. EFSA mandates labelling of these allergens on all food products.

The hygiene hypothesis / old friends hypothesis
Strachan/RookGraham Rook's refined "old friends" hypothesis: humans evolved with exposure to microorganisms (helminths, saprophytic bacteria, commensal organisms) that trained the immune system toward tolerance and T-regulatory cell responses. Reduced early-life microbial exposure in industrialised settings (C-section delivery, formula feeding, antibiotics, reduced farm exposure) shifts immune balance toward Th2 responses and IgE — the allergic phenotype. Explains the rise in allergy in HICs and among rural-to-urban migrants.