Hypersensitivity Reactions PDF

Hypersenstivity reactions Amira Abdelwhab Lecturer of Oral Medicine Allergy Definition: an altered reactivity of the tissue of certain individual caused by exposure to an allergen that is innocuous to other individual (on second contact with allergen). Allergen: antigen that can...

Hypersenstivity reactions Amira Abdelwhab Lecturer of Oral Medicine Allergy Definition: an altered reactivity of the tissue of certain individual caused by exposure to an allergen that is innocuous to other individual (on second contact with allergen). Allergen: antigen that can elicit allergic symptoms Allergen vs Hapten Proteins with HIGH molecular weight between. 5,000 and 40 , 000 Incomplete antigen that has LOW molecular weight. Allergen vs hapten Antigen  ^ Allergic ^ ^ reaction ^ Gell & Coombs classification 1970 of allergic reactions Type I: Anaphylaxis Type II: Cytotoxic reaction Immediate Type III: Arthrus reaction Type IV: Cell mediated Delayed (contact allergy) “ Sensitizing dose Allergic dose First exposure Re-exposure to an antigen to the antigen Sensitization Allergic of immune manifestations system Prevention of drug allergy 1) Medical history 2) Cross reaction (Penicillin and Cephalosporins) 3) Allergy testing 4) Route of administration Oral Parentral subcutaneous Intramuscular Intravenous 4. Medication Adrenaline First line in emergency. Anti-histaminics Produces action through drugs used but no bronchodil, v.c. & Corticosteroids (200 value in emergency decreasing capillary mg I.V) treatment. permeability. Anti-inflammatory Rapid action Immunosuppressant slowly acting and Dose: 0.5 ml (1\1000 Anti allergic antagonize one conc) I.M or S.C mediator only repeated every 5 min (histamine). (max: 1.5 ml) Never I.V?????? Type I allergic reaction Anaphylaxis Mechanism of anaphylaxis Release of mediators  Chemical mediators of anaphylaxis Histamine Prostaglandin vasodilation Capillary permeability bronchospasm Leukotreins  Generalized Localized anaphylaxis anaphylaxis Reactions involve one Number of organs are organ affected by immediate allergic reaction ❖ Bronchial asthma ❖ Anaphylactic shock ❖ Angioedema ❖ Hay fever ❖ urticaria Generalized anaphylaxis Definition Acute dangerous reaction that follows administration of foreign antigen or drug in sensitized person. It involves CVS, GIT, respiratory system and skin. The reaction usually starts within 30 minutes after injection of a drug. The quicker the onset, the more severe the reaction.  Face Pallor CNS Sweating Loss of Parasthesia consciousness Flushed face Angioedema Skin Urticara and itching Respiratory Wheezes due to CVS Rapid fall of bl. pressure bronchospasm Pulse is rapid and weak GIT Abdominal pain, Extremities vomiting & diarrhea Coldness of hands & feet Then later on patient become pulse-less, cyanotic and death may occur in a matter of minutes if not treated  Management Anaphylactic shock is a life threatening medical emergency because of: Bronchospasm Vasodilation Brain damage. First Position : supine position to increase cerebral blood flow Second: Administration of adrenalin immediately I.M ( 0. 3 - 0. 5 ml of 1:1000 dil  Third: Life saving measures ( O2 inhalation, I.V fluids ). Fourth: Administration of corticosteroids (Dexamethasone) Fifth: Call ambulance  Bronchial asthma Definition: It is an allergic disease characterized by recurrent attacks of acute breathlessness due to various substances inhaled or ingested. Allergic reaction result in release of LEUKOTREINS (Main mediator)  Bronchial asthma Mechanism 1. Spasm of smooth muscles of bronchi Interfere Patient with the allergic to flow of air a Release of 2.Swelling during substance leukotreins of inspiration inhaled or bronchial and ingested mucosa expiration 3.Exudate of mucous Swelling of mucosa Bronchial asthma Clinical manifestations Short forceful inspiration aided by accessory muscles of respiration. Long easily heard wheezing expiration. Face is pale nose ,lips and ears are cyanotic. The attack may last from an hour to several hours.  Bronchial asthma Dental implications 1. The patient should bring his medication ???????? 2. LA is better than GA & nitrous oxide is safe 3. Avoid aspirin ( leucotriens release) 4. Oral candidiasis in soft palate????? 5. Steroid supplementation if the patient is on systemic steroid  Bronchial asthma Management of attack in dental clinic 1. Stop dental procedure 2. Loosen tight cloths & remove any dental materials from the mouth 3. PABC 4. Self medication should be administrated (aerosol containing adrenaline)  Bronchial asthma 6. ,5 ml/ 1000 adrenaline SC or IM 7. Oxygen administration Antihistaminics Of no value; leucotriens are the mediators Slowly acting so no value in emergency Administrated to prevent relapse  Angioedema Definition: Angioedema is a condition characterized by rapid development of edematous swelling involving skin, subcutaneous and submucosal tissues in various parts of the body Angioedema Clinical picture Rapidly developing edema that may last several days Severe edema of the face involving lips around eye, chin and oral cavity Swelling smooth diffuse painless non inflammatory  Clinical picture Pruritis In severe cases there is laryngeal edema and death Treatment 1. Termination of dental procedure. 2. Position the patients in sitting. 3. Definitive Care : i –Asking for emergency medical care. ii –Adrenaline administration iii Administration of oxygen iv-Additional drugs : antihistaminics and corticosteroids administrated to prevent recurrence. v-Crico-thyrotomy: A totally obstructed airway may not be responed by adrenaline.Acrico-thyrotomy is the procedure of choice to establish an airway. Urticaria  Urticaria Definition: Common allergic reaction on skin varying from small localized papules to extensive large coalescing plaque which is erythematous and characterized by itching  Urticaria Mechanism release of Erythematous Drugs, food react with acting on histamine papules or certain IgE on mast superficial and other characterized bacteria cells vasculature by itching mediators  Urticaria Treatment Removal of cause Antihistaminics Corticosteroids Hay fever  Hay fever Definition: Seasonal allergic reaction to wind born pollen grains, food or dust (common in spring) Mechanism: Antigen antibody (IgE) reaction on the surface of mast cells with the release of histamine in m.m. of upper respiratory tract & conjunctiva  Hay fever Clinical feature Clinical features  Treatment Antihistamincs Desensitization: small repeated doses of the Ag are administrated to block IgE on mast cells (do not induce allergic reaction). Avoid causative agent Type II Hypersensitivity Reaction Cytotoxic Reaction  These reactions are IgG or IgM mediated. E.g: transfusion reaction caused by mismatched blood, drug induced hemolytic anemia and Thrombocytopenia Affect a variety of organs and tissues. Type III Hypersensitivity Reactions immune complex–mediated hypersensitivity  a. Serum Sickness - Definition : It is a self limiting allergic reaction caused by injection of protein or haptenic drug (penicillin). Mechanism: compleme direct nt fixation tissue & damage After 7 to 10 days, leukocytes (particularl produced antibodies attraction y will react with the vasculities slow residue of the and degradation circulating antigen arthritis). of antigen & forming antigen- injected the primary antibody complexes antigen antibody in small blood response is vessels initiated. Clinical manifestation: Itching followed by urticarial rash. Fever & Generalized lymphadenopathy. Swelling of joints leading to arthralgia. Edema in face, hands and feet. Asthma and rhinitis may occur. Peripheral neuritis, kidney disease and myocardial ischemia are less common features. Treatment: Corticosteroid Anti-histaminic for urticarial and adematous lesion  Stomatitis Medicamentosa (Allergic Stomatitis) Definition: Allergic stomatitis are eruptive lesions of the oral mucosa resulting from SYSTEMIC administration of allergen. The allergic manifestation may occur in the mouth or skin or both. The oral manifestation are less common than that the cutaneous lesion (dermatitis medicamentosa). Oral manifestation: Acute multiple vesicles and ulcers similar to erythema multiforme. Angioedema Urticaria of the lip Fixed drug eruption that appear at the same site when the drug is taken (tongue is a common site)  Type IV-Hypersensitivity Reaction Stomatitis Venenata \Dermatitis Venenata (Contact Allergy)  Definition It is a DELAYED allergic reaction of skin or oral mucosa to LOCAL contact with foreign substance (allergen). Dermatitis venenata→ skin. Stomatitis venenata→ oral cavity Manifestations appear 24-48 hrs after second exposure.  Pathogenesis First contact with antigen and epithelial cell protein T cell sensitization Second contact with antigen release of cytokines by sensitized T-cell and tissue damage at the site of local contact. The oral mucosa is less liable to sensitization compared to skin ???????????? a ) Less number of Langerhans cells. b) Saliva. c ) High vascularity of submucosa d) Allergen is only in brief contact with oral mucosa. e ) keratin layer in skin provides a good supply of protein to combine with hapten forming antigen complex Contact stomatitis can be induced by  Clinical features Erythema ,edema and in severe cases ulceration of the site of contact Itching is a characteristic complaint of the skin and burning in the oral mucosa. Cheilitis ,dry scalled lip and localized atrophy of tongue coating  Clinical features Dermatitis venenata may affect perioral skin (itching, erythema vesicles and ulceration, urticaria ). The use of vinyl gloves as latex substitute has minimized the occurrence of allergic reactions Diagnosis 1 –Case history 2 –Clinical examination: the reaction occurs at the site of local contact. 3 –Patch test :Performed on skin or oral m. m. Dermal test : The allergen ( e. g. scrapping of denture ) is applied to the skin with moist gauze on one arm and control moist gauze on other side. Allergic individuals show wheel (erythema ) within 24-72 hours at site of contact.Erythema ,sloughing or ulceration indicated a positive patch test.  Epimucous test The allergen is applied to the m.m. via orabase For testing allergic reaction to acrylic denture, either covers the denture with tin foil leaving small area uncovered or cover a small area of the denture with tin foil. Positive patch test means erythema or ulceration is developed on the area of contact within 24-72hrs. Treatment 1.Mild: elimination of the cause. 2.Severe : a ) Antihistaminics. b) Steroid (topical or systemic ). 3 Symptomatic : a )Antiseptic agent to minimize 2ry infection. b)Topical anesthetic to relief pain. Thank you