Allergy Flashcards
What is an allergy?
acquired hypersensitive state resulting from an immunologic rxn to a non-infectious foreign substance
What are the 4 types of allergic reactions? Give names
- anaphylactic
- cytotoxic or antibody mediated
- immune complex
- delayed hypersensitivity
Give the sequence of events for a type 1 reaction
Occur within seconds
Begin at periphery (skin, mucosa) and progress to eyes, nose, GI, followed by respiratory and cardiovascular complications
What immune cells modulate the type 1 reaction?
IgE antibody response leading to degranulation of histamine from mast cells
What is the MOA of histamine?
- vasodilation
- edema
- increased mucus production
- itching
- redness, pain
- contraction of smooth muscle (lungs)
What reactions in type 1 reaction lead to it being life threatening?
laryngeal edema & bronchospasm affect airway
circulatory collapse & cardiac arrest
What are common agents that can cause a type 1 rxn?
Antibiotics
Bee stings
Milk
Eggs
What immune cells modulate the type 2 reaction?
IgM or IgG
Antibodies bind to host cell antigens they recognize as foreign
The antibodies then act as an opsonin by also binding a macrophage inducing the macrophage to phagocytose the target cell. Or the antibody can activate the complement pathway
Or antibody can bind lymphocyte
What type of agents can cause a type 2 hypersensitivity?
Penicillin, thiazide, cephalosporins,
Pts may report hx of blood transfusions
Give example of type 2 hypersensitivity rxn
Goodpasture syndrome
Antibodies bind to basement membrane antigens and attack BM of the lungs and kidneys causing organ fauilure
What immune cells modulate the type 3 reaction?
Antibody mediated via the formation of an immune complex (aggregate of antigen + antibody) which activate complement
What is the MOA of a type 3 reaction which causes the symptoms?
The immune complex will precipitate in various tissues such as skin, joints, vessels, and glomeruli. Complement activation leads to monocytes and neutrophils releasing lysosomal enzyme and free radicals causing tissue damage
usually happens in the vessels and causes vasculitis
Give an example of a type 3 hypersensitivity rxn
Serum sickness
Can be triggered by certain drugs such as vaccines, abx or by insect bites
Systemic lupus erythematosus
What immune cells modulate a type 4 hypersensitivity rxn?
NOT antibodies, cell-mediated reaction
T helper cells or cytotoxic t cells which are sensitized will bind the antigen
T cells release cytokines which cause tissue damage
T CELLS WILL ALSO RECRUIT ACTIVATE MACROPHAGES WHO DESTROY TISSUE
Give an example of type 4 hypersensitivity rxn
Contact dermatitis
Tuberculin skin test
Latex (can be type 1 or 4)
What is the difference between types 1-3 and type 4?
Types 1-3 are immediate rxns because they occur within 24 hrs
type 4 is delayed because it occurs more than 12 hrs after exposure and usually between 48-72 hrs
What type of individual has an impaired allergic response?
Since patients with acquired immunodeficiency syndrome (AIDS) have a progressive decline in the number of CD4 cells, they also have a defective type four hypersensitivity reaction
What is the prevalence of contact dermatitis?
1-6%
How do you manage a type 4 reaction?
Antihistamince cream, benadrly, stop the exposureq
what hypersensitivity rxns are we worried about in dentistry
1 and 4
What are the two types of local anesthetics and which kind are patients more likely to be allergic to?
Amides = lidocaine, mepivacaine, prilocaine Esters = procaine (novocaine) no longer in use
Really the only ester in use is topical benzocaine
ppl way more likely to be allergic to esters
Metabolism of local anesthetics
Amides = biotransformed in the liver (except for atricaine which is unique and is broken down similar to esters
Esters = hydrolyzed in the bloodstream by plasma esterases
Are allergies to local anesthetics common?
No, usually when pt reports an allergy to local anesthetics you should be suspicious that i was syncope or cardiac palpitations attributed to epinephrine contained either in the solution or released endogenously
Allergic reactions to anesthetics are typically not due to the anesthetic but are due to the preservatives (methylparaben) or antioxidants (sulfites)
Methylparaben is included in multidose vials ONLY
Sulfites prevent the oxidation of vasopressors
what is the incidence of parasteshia with articaine?
Garisto: Compared to other local anesthetics, paresthesia was found to be 7.3 times more likely with 4% articaine and 3.6 times more likely with 4% prilocaine
How do you recognize anaphylaxis?
skin rash (hives, itchiness, flushing), angioedema, wheezing, laryngeal edema, hypotension, respiratory and circulatory depression, CNS depression (loss of consciousness, confusion, headache), vomiting fatal unless immediate action is taken
How do you handle anaphylaxis?
- Activate EMS
- Patient in supine position
- Inject 0.3 - 0.5 mL of epinephrine (1:1000) IM or subcutaneously. 0.15 mL for children
- Repeat if needed every 3-5 min
- Administer 100% oxygen at 10L/min
- Consider 50 mg Benadryl IM or IV
- CPR as needed
What dental materials can cause allergic reaction?
topical anestethics, amalgam, acrylic, toothpastes
Is a Ti allergy a thing?
prevalence of 0.6%
What is the prevalence of a penicillin allergy? How many of those people are allergic to cephalosporins?
5-10% of people allergic to penicillin
Cephalosporins cross react in 5-10% of penicillin sensitive patients
