A disorder of the immune system often also referred to as
atopy (a predisposition to an immune response against
diverse antigens and allergens leading to CD4+ Th2
differentiation and overproduction of immunoglobulin E
Strictly, allergy is one of four forms of hypersensitivity
and is called type I (or immediate) hypersensitivity.
Allergic reactions occur to normally harmless
environmental substances known as allergens.
Reactions are acquired, predictable, and rapid Include
eczema, hives, hay fever, asthma attacks, food allergy, and
reactions to drugs and the venom of stinging insect such
as wasp and bees
3. HYPERSENSITIVITY REACTIONS
Excessive, undesirable (damaging, discomfort
producing and sometimes fatal)
reactions produced by the normal immune system.
Require a pre-sensitized (immune) state of the host
Gell-Coombs Classified the reactions into four
types based on the mechanisms involved and time
taken for the reaction
Type I, type II, type III and type IV
Produce tissue injury
4. HYPERSENSITIVITY TYPES AND IMMUNE
3 involve antibody
Type I (immediate): mediated by IgE (Mast Cells)
Type II: mediated by IgG or IgM
TypeIII (immune complex disease):
IgG & complement
One involves antigen specific cells-
Type IV: Delayed type hypersensitivity, cell-
mediated immune memory response.
5. TYPE I HYPERSENSITIVITY
Known as immediate or anaphylactic hypersensitivity
Sudden, widespread, potentially severe and life-
threatening allergic reactions.
Involve skin, eyes, nasopharynx bronchopulmonary
tissues and gastrointestinal tract
The reaction usually takes 15 - 30 minutes from the
time of exposure to the antigen
Begin with a feeling of uneasiness, followed by
tingling sensations and dizziness.
Rapidly develop severe symptoms, including
generalized itching and hives, wheezing and
difficulty breathing, fainting, or a combination of
these and other allergv symptoms.
6. TYPE I HYPERSENSITIVITY REACTIONS
An acute multi-system severe type I hypersensitivity
reaction that can cause shock, or even death Injection
Inhaled/Airborne Allergic runny nose:
Irritation and inflammation of some internal areas of the
nose Asthma - lower airways
Wheal and flare allergy: skin reaction which occurs in
response to exposure to an allergen. This distinctive
reaction is often used in testing for allergies to determine
which allergens trigger a reaction in a patient.
A rash that is caused by an adverse reaction to certain
substances. In most cases, allergy hives can be traced
to certain foods or injections
7. TYPE II HYPERSENSITIVITY
Known as cytotoxic hypersensitivity
• The antigens are normally endogenous, although
exogenous chemicals can also lead to type II
• Autoimmune thrombocytopenia, autoimmune
hemolytic anemia, Rh disease of the newborn
• The lesion contains antibody, complement
• The reaction time is minutes to hours.
• Primarily mediated by antibodies of the IgM
or IgG classes and complement
• Antibody IgG mediates cell death.
8. TYPE III HYPERSENSITIVITY
Immune complex hypersensitivity
The reaction may be general or may
involve individual organs including skin,
kidneys, lungs, blood vessels, joints (e,g.
rheumatoid arthritis) or other organs
This reaction may be the pathogenic
mechanism of diseases caused by many
The reaction may take 3 - 10 hours after
exposure to the antigen
9. TYPE IV HYPERSENSITIVITY
Known as cell mediated or delayed type
The reaction takes two to three days to develop.
The classical example is tuberculin reaction
Involved in the pathogenesis of many autoimmune
and infectious diseases
tuberculosis, leprosy, blastomycosis (fungal
infection), toxoplasmosis (a parasitic disease).
garanulomas due to infections and foreign antigens.
contact dermatitis (poison ivy, chemicals, heavy metals, etc.)
Can be classified into three categories depending on
the time of onset and clinical and histological
11. DIAGNOSTIC TESTS FOR IMMEDIATE
• Skin (prick and intradermal) tests
• Measurement of total IgE and specific IgE
antibodies against the suspected allergens.
• Total IgE and specific IgE antibodies are
measured by a enzyme immunoassay (ELISA).
• Increased IgE levels are indicative of an atopi
• A genetic predisposition for atopic diseases (Atopic
dermatitis, allergic rhinitis, and asthma)
12. SKIN PRICK TEST
Skin prick testing is cheap, rapid and accurate
High degree of specificity Safe and
Wide range of allergens
Objective evidence of sensitization
13. TECHNIQUE AND REACTION
Introduction of allergen
extract into the dermis
Use the inner forearm
Mark the area to be tested (2 cm apart)
Place a drop of each allergen extract on each mark
Prick the skin through the drop
Use a new lancet/needle for each allergen
Negative (saline solution) and positive control
(histamine phosphate, 10 mg/ml) must be included: to
exclude false positive reactions (dermographism) and
false negative reactions (intake of antihistamines)
15. Put drops of allergen extracts
on the skin
Prick the skin through the
Read at their peak (15-20 minutes)
Measure with a millimeter rule
Largest + smallest of wheal and erythema
The wheal is principally used (diameter)
What if the negative control is positive?
What if the positive control is negative?
The size of the wheal does not relate to the severity of
17. COMMON ERRORS IN PRICK TESTING
Tests too close together (< 2 cm)
Induction of bleeding, leading possibly to false-positive
Insufficient penetration of skin by lancet leading to
Spreading of allergen solutions during the tests.
18. CAUSES OF FALSE-POSITIVE SKIN PRICK TESTS
Contamination of an allergen extract
Enhancement from a nearby strong reaction
19. CAUSES OF FALSE-NEGATIVE SKIN PRICK
Extract of diminished potency
Medications modulating allergic reaction
Diseases attenuating the skin response, e.g. eczema
Improper technique (no or weak puncture)
20. FACTORS AFFECTING SKIN TEST RESULTS
Quality of the allergen extract (standardized)
Area of the body, wrist least reactive
Age, less reactive after 50
Circadian rhythms do not affect the skin reaction
Drugs: short acting antihistamines inhibit the
wheal-and-flare reaction for up to 24 h; long-
acting antihistamines may affect reaction for up 4-5
21. NURSING ASSESSMENT
• Physical examination
• History collection
• Assess any kind of allergy. The nurse must assess all
patients for allergies or previous reactions to
• Assess patient’s knowledge. The nurse must also
assess the patient’s understanding of previous
reactions and steps taken by the patient and the
family to prevent further exposure to antigens.
• New allergies. When new allergies are identified,
the nurse advises the patient to wear or carry
identification that names the specific allergen or
22. NURSING DIAGNOSIS
Impaired gas exchange related to ventilation
Altered tissue perfusion related to decreased blood
flow secondary to vascular disorders due to
Ineffective breathing pattern related to the swelling
of the nasal mucosa wall.
Acute pain related to gastric irritation.
Impaired skin integrity related to changes in