1. Atopy
    the genetic tendency to develop a hypersensitivity reaction to common environmental substances (allergens)

    • High degree of heritability & concordance
    • among twins
  2. popularity: urticaria, asthma, allergic rhinitis
    • –Allergic
    • rhinitis > urticaria > asthma
  3. rish inc for Atopy with...
    a + GHx ((esp if both parent are atopic)
  4. aeroallergens
    ◦Seasonal pollens (grass pollens, ragweed)

    ◦Outdoor molds (airborne fungi)

    ◦Indoor allergens (indoor fungi, animal dander, dust mites, insects)
  5. hay fever - clinical aspect
    ◦Sneezing, rhinorrhea (clear secretions), nasal congestion, itching in the nose & palate

    • ◦Less common signs: conjunctivitis
    • (allergen must be blown into the eyes), fatigue, arthralgia, myalgia, cognitive
    • changes (esp in children) - these are mostly cytokine-mediated effects

    ◦Other: obstruction of sinus ostia causing acute (bacterial) sinusitis
  6. hay fever - mng
    • ◦Avoidance of the allergen is the best
    • intervention

    ◦First-line therapy: antihistamines - first generation formulas reduce motor skills, second generation compounds are better

    • ◦Immune therapy: anti-IgE (omalizumab) -
    • effective but $$
  7. hives
    pruritic (itchy), erythematous (red) & blanching (loose color with pressure) skin papules (slightly raised bumps!) 

    ◦Shape: round or oval with pale raised centers (wheals)

    ◦Size: varies from several millimeters to a few centimeters
  8. itching is cause by
    • ◦immediate release of histamine, leukotrienes
    • & PGs from mast cells (vasodilitation, leakage of plasma from venules)
  9. Angioedema
    involves non-pitting edema of lips, tongue, eyelids, hands, feet or genitalia 

    ◦May involve the oropharynx & larynx

    ◦No report of itching but may feel burning or pressure (stretching)

    • ◦Swelling involves a delayed reaction caused by inflammatory cytokines released in
    • subcutaneous or submucosal tissues
  10. Chronic recurrent hives or angioedema over 6 weeks - clinical aspect
    ◦Food – requires chronic exposure (i.e., wheat)

    ◦Physical – triggered by scratching, exercise, exposure of skin to heat, ice, vibration, pressure, UV radiation, chronic infections (sinusitis, dental abscess, H. pylori)

    ◦Immune-mediated – during flares of autoimmune diseases such as rheumatoid arthritis, Hashimoto’s thyroiditis

    ◦Complement-mediated - Hereditary Angioneurotic Edema
  11. Acute hypersensitivity rxn - clinical aspect and tx
    5-30 minutes after ingesting a drug or food or insect bite, but may also be idiopathic


    • ◦Acute cases are self-limited; antihistamines
    • can prevent recurrent attacks

    • ◦Antileukotriene
    • medications or corticosteroids may become
    • necessary for severe or chronic cases


    • ◦Acute cases are self-limited; antihistamines
    • can prevent recurrent attacks

    • ◦Antileukotriene medications or corticosteroids may become
    • necessary for severe or chronic cases
  12. Hereditary Angioneurotic Edema
    • ◦An autosomal dominant
    • trait

    ◦Involves a deficiency of C1 esterase inhibitor - a regulatory protein that controls and limits complement activation, fibrinolysis & bradykinin production – it is this latter process that causes capillary leakage and edema
  13. Hereditary Angioneurotic Edema - clinical features
    ◦Mild attacks may begin in infancy but become severe at puberty

    • ◦Swelling is spontaneous or precipitated
    • by pressure, trauma, stress
  14. Hereditary Angioneurotic Edema - tx
    no tx

    ◦Epinephrine is only modestly effective

    • ◦Other approaches may include
    • antihistamines, attenuated androgens, transfusion with FFP

    • Acute attacks may require nasotracheal
    • intubation
  15. Systemic Anaphylaxis
    Immediate and life-threatening  hypersensitivity reaction

    • Allergy mediators are found in multiple organs
    • –Skin: urticaria, angioedema, flushing
    • –Respiratory:laryngeal edema, bronchospasm
    • –CV:hypotension, arrhythmia, 
    • –GI:nausea, vomiting, gastrointestinal spasms

    • Most common allergens are drugs, insect venoms, foods, radiocontrast media & latex
    • ◦Allergen exposure must lead to sensitization before an immediate hypersensitivity can occur
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