Allergy basic

Allergy
By :
Vaidehi D. Shah
B Pharm IV Sem
SMT BNB Swaminarayan Pharmacy College , Salvav ,Vapi.
SMT BNB SWAMINARAYAN PHARMACY COLLEGE , SALVAV ,VAPI 1

ALLERGY
It is defined as hypersensitivity of the immune system to typically harmless
substance in the environment.
 The word allergy is derived from the Greek words :
“allos” meaning different or changed
“ergos” meaning work or action
 Allergy roughly refers to an “altered reaction”.
 Allergy – producing substances are called as “Allergens”.
 Allergic reactions occur when a person’s immune system reacts to normally
harmless substances in the environment.

HISTAMINE:
It is first line mediator producing inflammatory response.
It is stored in : (a) Mast cells
(b) Basophils
(c) Platelets
Mast cell are richest source of histamine.
They are stored as granules & released by degranulation in injury.
They act via :
H1 receptor – In smooth muscle & blood vessels
H2 receptor – In stomach (Enterochromaffin cells)
H3 receptor – Between neurons (Synaptic cleft)

Main Actions are :
(a) Vasodilation of blood vessel’s cells
(b) Increase vascular permeability
(c) Smooth muscle contraction
(d) Itching
(e) Pain
(f) Produce immune response like allergy, hypersensitivity, etc.

DISEASES DUE TO ALLERGIC REACTIONS:
Hay fever
Atopic dermatitis
Allergic asthma
Anaphylaxis
(1)Hay fever (allergic rhinitis):
It is due to indoor allergens , such as dust mites , molds and pollens .
Symptoms result from the inflammation of the tissues that line inside the
nose (mucus lining or membranes) after allergens are inhaled.
Adjacent areas, such as the ears , sinuses, and throat can also be involved.

(2)Atopic dermatitis:
It is severe form of eczema , which is an umbrella term used to describe a
group of conditions that result in itchy , red , and irritated skin.
It results due to genetic and environmental factors.
(3)Allergic Asthma:
It is a breathing problem results from the inflammation and spasm of the
lung’s air passages(bronchial tubes) due to certain allergens.
Thus due to narrowing of air passages, air flow inside and outside of lungs is
limited.
(4)Anaphylaxis:
It is life – threatening reaction that affect no. of organs at same time due to
certain allergens.
In this , blood vessels became dilated and leaky , thus result in drop in blood
pressure.

AFFECTED ORGAN COMMOM SIGNS AND SYMPTOMS
Nose Swelling of nasal mucosa , runny nose , sneezing
Sinuses Allergic sinusitis
Eyes Redness and Itching of conjunctiva
Airways Sneezing , coughing , bronchoconstriction , wheezing , dyspnea
Ears Pain , Impaired hearing
Skin Rashes
GIT Abdominal pain , bloating , vomiting , diarrhea
SIGNS AND SYMPTOMS:

CAUSES:
GENETIC
Heredity
Race
Sex
Age
ENVIRONMENTAL
Infectious disease
during childhood
Allergens
Pollution
Dietary changes

(1)Hereditary:
The hereditary is often cause of allergy, which means it can be passed through
genes from parents to their kids.
(2)Race (Human Categorization):
Race have shown a particular role in children’s sensitivity to developing
allergies.
For ex: African – American children were sensitized to at least one food allergen
three times more often than caucasian children.
(3)Sex :
Allergy may be occurred during sexual intercourse. It could be due to latex
condom, seminal fluid, vasomotor rhinitis, etc.

(4)Age :
Allergy can develop increasing with increase in age as there are changes in the
immune system that are a natural part of aging.
(5)Pollution :
Pollutants most importantly tobacco and smoke is associated strongly with
allergic reactions by enhancing body’s ability to produce IgE.
(6)Dietary Changes :
Changing your diet may cause food allergies as it can lead immune system to
identify some of proteins in food as harmful.

Inhalant Allergen
Ingestant Allergen
Injectant Allergen
Contactant Allergen
Infectant Allergen
Types of Natural Allergens:
(8)Allergens:

(a)Inhalant allergens:
Causes allergy by entering in respiratory tract .
Ex: Air particles like -
pollens , dust , mites , mould spores , etc.
(b)Ingestant allergens:
Causes allergy by entering in gastrointestinal tract.
Ex: Certain foods like –
cow’s milk , peanuts , soyabean , tree nuts, fish , shellfish , etc.
(c)Injectant allergens:
Causes allergy due to their injection in skin surface .
Ex : Certain medications like –
penicillin injections leads to anaphylactic reactions in some people.

(d)Contactant allergens:
Causes allergy due to coming in contact with body.
Ex : poison ivy , eastern and western poison oak , poison dogwood , etc.
(e)Infectant allergens:
Causes allergy by presence of metabolic products of living microorganisms
in body.
Ex : Living microorganisms like –
bacteria , protozoa , hookworms , tapeworms , etc.

MECHANISM OF ALLERGY:
Allergens from environment
Binds to IgE antibodies i.e. part of body’s immune system
Afterwards binds to a receptor on mast cells or basophils
Triggers the release of inflammatory chemicals such as histamine
Thus causing hypersensitive response to harmless substances

Fig.: Mechanism of Allergy

DIAGNOSIS:
(1)Skin testing:
Also called as puncture or prick testing.
Tiny pricks , punctures in skin is
made
Introduce allergens into pricked
skin
If inflammation visible in 30
minutes
Then , it is allergic patient.

(2) Blood testing:
Blood sample is taken
Multiple allergens are tested
on same blood sample
Thus , safe as patient are not
exposed to allergens.

PREVENTION :
Avoid known allergens.
Early exposures to potential allergens.
TREATMENT:
Steroids
Anti-histamines
Epinephrine
Mast cell stabilizers
Anti-leukotrienes

References:
• Harsh Mohan; Text book of Pathology; 6th edition; India; Jaypee Publications;
2010.
• V. Kumar, R. S. Cotran and S. L. Robbins; Basic Pathology; 6th edition;
Philadelphia; WB Saunders Company; 1997.
• Laurence B, Bruce C, Bjorn K. ; Goodman Gilman’s The Pharmacological Basis
of Therapeutics; 12th edition; New York; McGraw-Hill; 2011.

Thank You

Allergy basic

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