Allergy

Question 1

Define allergy.

Answer 1

Allergy is an altered reactivity of the tissues of a certain individual caused by exposure to an agent (allergen).

Question 2

What are the different routes through which an allergic response to an allergen can occur?

Answer 2

Inhalation, ingestion, injection, and contact with skin.

Question 3

What is the Gell & Coombs classification of hypersensitivity reactions?

Answer 3

Hypersensitivity reactions are classified into four groups: Type I (anaphylactic), Type II (cytotoxic), Type III (immune complex), and Type IV (delayed-type).

Question 4

Describe the mechanism of Type I hypersensitivity reaction.

Answer 4

First contact with allergen forms IgE, which binds to mast cells. Upon subsequent contact, antigen binds to IgE on mast cells, causing their destruction and release of vasoactive amines.

Question 5

What substances are released during a Type I hypersensitivity reaction?

Answer 5

Preformed granules (heparin, histamine, proteolytic enzymes, PAF, neutrophil chemotactic factor, eosinophilic chemotactic factor) and newly synthesized substances (leukotrienes, prostaglandins).

Question 6

What are the effects of the mediators released in a Type I hypersensitivity reaction?

Answer 6

Vasodilatation, increased capillary permeability (edema), contraction of bronchial smooth muscles (asthma), and immediate clinical manifestations within half an hour. Mucous and sensory

Question 7

Provide examples of localized anaphylaxis.

Answer 7

Urticaria, angioedema, asthma, and hay fever.

Question 8

What are the clinical features of generalized anaphylaxis?

Answer 8

Generalized vasodilatation, severe hypotension, shock (potentially fatal), and multiple organs affected.

Question 9

What is anaphylactic shock?

Answer 9

A generalized anaphylactic reaction affecting multiple systems (skin, eyes, GIT, cardiovascular, respiratory) leading to life-threatening symptoms.

Question 10

What are the causes of anaphylactic shock?

Answer 10

Allergy to drugs (e.g., local anesthetics, penicillin), food, and parenteral drug administration.

Question 11

List the signs and symptoms of anaphylactic shock.

Answer 11

Itching, burning skin, swelling of face and tongue, laryngeal edema, weak rapid pulse, low blood pressure, dizziness, nausea, vomiting, diarrhea, abdominal cramps, chest tightness, difficulty breathing, respiratory wheezing, loss of consciousness, cyanosis, and death.

Question 12

How is anaphylactic shock managed during the life-threatening phase?

Answer 12

Administer adrenaline (epinephrine) 1:1000 I.M (0.01 mg/kg), position patient flat with legs raised, and provide oxygen.

Question 13

What are the steps to prevent recurrence of anaphylactic shock symptoms?

Answer 13

hydrocortisone 200mg IV/IM, antihistaminic, IV fluids, Airway

Question 14

What is angioneurotic edema?

Answer 14

Rapid development of edematous swelling involving skin, subcutaneous and submucosal tissues in various parts of the body.

Question 15

What are the causes and triggers of angioneurotic edema?

Answer 15

Blunt injury, trauma from dental procedures, emotional stress, and injection of drugs.

Question 16

How is angioneurotic edema managed?

Answer 16

mild: antihistamins (cortst. If moderate), severe: adrenaline 1:1000

Question 17

Define urticaria.

Answer 17

An immediate localized reaction involving the superficial blood vessels.

Question 18

What is the etiology of urticaria?

Answer 18

Food ingestion by an allergic individual.

Question 19

How is urticaria treated?

Answer 19

Removal of the causative factor, antihistaminics, and corticosteroids.

Question 20

Define bronchial asthma as an allergic disease.

Answer 20

An allergic disease characterized by recurrent attacks of acute breathlessness.

Question 21

What is the mechanism of bronchial asthma?

Answer 21

Allergic reaction results in the release of leukotrienes (SRS-A) which causes bronchial smooth muscle contraction.

Question 22

What are the clinical features of a bronchial asthma attack?

Answer 22

Sudden onset of short forceful inspiration, wheezing expiration, inability to deflate the chest, pale face, cyanotic nose, lips, and ears.

Question 23

How is bronchial asthma managed during an attack?

Answer 23

Stop dental procedure, check airway, loosen tight clothing, sit patient upright, ensure airy and cool room, humidified oxygen inhalation, and provide medication (salbutamol inhalation, systemic glucocorticosteroids, epinephrine, IV fluids).

Question 24

Describe the mechanism of Type II hypersensitivity reaction.

Answer 24

Antigen attaches to cell surface (e.g., RBCs, WBCs, platelets) and reacts with circulating antibodies (IgG or IgM) leading to complement activation and cellular damage or lysis.

Question 25

Give examples of Type II hypersensitivity reactions.

Answer 25

Incompatible blood transfusion, Rh incompatibility, drug-induced immunological reactions, and autoimmune diseases (e.g., pemphigus vulgaris).

Question 26

Question: What is a hapten and why can’t it elicit an immune response on its own? When can it elicit a response?

Answer 26

Answer: A hapten is a low-molecular-weight compound that can be bound by antibodies but cannot elicit an immune response on its own. It is non-immunogenic until it binds with a larger carrier immunogenic molecule, forming a hapten-carrier complex that can act as an immunogen and induce an immune response.

Question 27

Question: How do drugs obtain immunogenicity and what is the consequence of this process?

Answer 27

Answer: Drugs, being low-molecular-weight compounds, are considered haptens (or proantigens) and do not elicit an immune response on their own. When they enter the body and bind to a body protein, they form a “drug-body protein conjugate.” This complex, due to its increased molecular weight and complexity, can elicit an immune response. The immune system targets the drug part of the complex, which can result in unwanted effects such as allergic reactions. Penicillins are a common example of such drugs.

Question 28

Describe the mechanism of Type III hypersensitivity reaction.

Answer 28

Soluble antigen forms antigen-antibody complexes (IgG or IgM) that precipitate in or around blood vessels, causing complement activation, inflammation, and tissue damage.

Question 29

Provide examples of Type III hypersensitivity reactions.

Answer 29

Serum sickness and stomatitis medicamentosa (allergic stomatitis).

Question 30

What is serum sickness?

Answer 30

An allergic reaction occurring 7 to 10 days after a large dose of injected antigen (foreign serum) or haptenic drug, resulting in antigen-antibody complexes causing vasculitis and arthritis.

Question 31

What is stomatitis medicamentosa?

Answer 31

An allergic eruption of the oral mucosa resulting from systemic administration of an allergen (drugs or food).

Question 32

Describe the mechanism of stomatitis medicamentosa.

Answer 32

Humoral antibodies mediate the allergic reaction, with the allergen administered via injection, ingestion, or percutaneous absorption.

Question 33

What are the oral manifestations of stomatitis medicamentosa?

Answer 33

Acute multiple vesicles and ulcers similar to erythema multiforme, and fixed drug eruption, commonly on the tongue.

Question 34

Define Type IV hypersensitivity reaction.

Answer 34

A delayed allergic reaction of the skin or oral mucosa to local contact with a foreign substance (allergen).

Question 35

What is the mechanism of Type IV hypersensitivity reaction?

Answer 35

First contact sensitizes T cells through antigen processing, leading to memory cell development. Second contact triggers T cell proliferation and release of lymphokines, causing tissue destruction.

Question 36

Why is oral mucosa less liable to sensitization compared to skin?

Answer 36

Brief contact with allergens, dilution and digestion by saliva, and high vascularity of submucosa leading to rapid absorption and dispersion of allergens.

Question 37

What are the clinical features of stomatitis venenata?

Answer 37

Burning and itching at the contact site, erythema, edema, vesicles, ulcers, localized tongue coating atrophy, cheilitis, and angular cheilitis.

Question 38

What are the clinical features of dermatitis venenata?

Answer 38

Itching, burning, erythema, vesicles, or urticarial rashes on perioral skin, and dermatitis on dentist’s or technician’s fingers.

Question 39

How is stomatitis venenata/dermatitis venenata treated?

Answer 39

Eliminate causative agents, corticosteroids for severe cases, and symptomatic treatment (antiseptic agents, topical anesthetics).

Question 40

What is the difference between allergic stomatitis and contact stomatitis?

Answer 40

Allergic stomatitis involves systemic administration and Type III hypersensitivity, while contact stomatitis involves topical administration and Type IV hypersensitivity.

Question 41

Explain cross-reaction in drug allergies.

Answer 41

Allergy develops to chemically related drugs with the same basic nucleus; for example, patients allergic to procaine may also be allergic to sulfa drugs.

Question 42

How does adrenaline act in the treatment of hypersensitivity reactions?

Answer 42

Acts as a bronchodilator, vasoconstrictor, and reduces capillary permeability, increasing blood pressure and stimulating heart muscle.

Question 43

why are corticosteroids used in treating hypersensitivity reactions?

Answer 43

Used as anti-inflammatory and immunosuppressant agents in allergic diseases.

Question 44

Why are antihistamines not suitable for emergency treatment of hypersensitivity reactions?

Answer 44

They are slow-acting and only antagonize one mediator (histamine).

Question 45

What preventive measures can minimize the risk of drug allergies?

Answer 45

Take a careful history of previous drug reactions and allergic conditions, avoid IV administration when possible, observe high-risk patients post-administration, and equip dentists to handle allergic reactions.

Question 46

What are the clinical presentations of various hypersensitivity reactions?

Answer 46

Localized and generalized anaphylaxis, urticaria, angioedema, bronchial asthma, and other symptoms based on the type of hypersensitivity reaction.

Question 47

How is a treatment plan formulated for hypersensitivity reactions?

Answer 47

Identify the type of reaction, manage immediate life-threatening symptoms (e.g., adrenaline for anaphylaxis), use antihistamines and corticosteroids as needed, and prevent recurrence.

Question 48

What is the diagrammatic representation of hypersensitivity reactions?

Answer 48

Diagrams illustrating the mechanisms of Type I, II, III, and IV hypersensitivity reactions.

Question 49

Summarize the key points of hypersensitivity reactions.

Answer 49

Hypersensitivity reactions are classified into four types, each with distinct mechanisms, clinical presentations, and management strategies.

Question 50

How would you integrate knowledge of hypersensitivity reactions into clinical scenarios?

Answer 50

Apply understanding of mechanisms, symptoms, and treatment plans to diagnose and manage allergic reactions in patients effectively.