1. Allergens are substances that can sensitize the body and cause an unusual immune response in hypersensitive individuals. Common allergens include proteins or glycoproteins from pollens, dusts, foods, insects, and medications. 2. Allergens can be classified based on their route of exposure - inhalant allergens cause respiratory symptoms, ingestant allergens cause gastrointestinal issues, injectant allergens are from insect stings, contact allergens touch the skin, and infectant allergens are from microbes. 3. Common examples of allergens include pollen, dust mites, animal dander, certain foods like milk or shellfish, bee

1. Topics Of Discussion:-
1.Introduction To Allergens
2.Types Of Allergens

2. • Allergens are inciting agents of allergy, i.e. the substances
capable of sensitising the body in such a way that an
unusual response occurs in hypersensitive person.
• Allergen may be biologic, chemical or of synthetic origin.
• It is common to speak about the substances, such as
pollens, danders, dust, etc., as natural allergens. Although
the chemical identity of allergen is unknown, but most
known allergens are protein or glycoprotein and do not
have much difference from other immunogens except
perhaps being somewhat smaller in size (mol wt. 10,000–
70,000). Most allergenic substances are mixture in
composition.
Sneezing
Eczema

3. WHAT IS ALLERGY?
The term allergy means changed reactivity and is an abnormal response of organism to an external agent
such as pollen of some plants, dust, pests, insect bites, certain drugs, food and other
allergens.Sneezing is always considered to be a symptom of a cold but sometimes it is an allergic reaction
to some thing in the air. According to reports available approximately 30% population suffers from some sort
of allergic syndrome. However, few persons develop symptoms that are sufficiently severe to require
the services of allergist or physician. The occurrence of allergic disease is determined by the
characteristic of the individual as well as those of the allergen and even the condition of exposure.
Following are predisposing factors which make the person hypersensitive to allergens:
•Hereditary tendency to allergic response
•Dysfunction of the endocrine glands
•Increased excitability of sympathetic and parasympathetic nervous systems
•Absorption of metabolic and catabolic substances
•Hepatic dysfunction and
•Psychic influences

4. How does allergy occurs?
Allergy is the result of mistaken identity. An allergen enters the body and is wrongly identified
by the immune system as a dangerous substance. In response, the immune system makes
antibodies to attack the allergen. These are specific antibodies of the IgE (immunoglobulin E)
class.
When an allergen is found, IgE antibodies trigger a cascade of immune system reactions,
including the release of chemicals known as mast cell chemicals. These are substances that
the body normally uses to destroy micro-organisms. The most common of these is histamine.
In small amounts, histamine causes itching and reddening of the local area. In large amounts,
the nearby blood vessels become dilated and the area swells with accumulated fluid.
The immune system’s tendency to overreact to a harmless substance is thought to be genetic.
The term ‘atopy’ describes this genetic tendency.

5. Types Of Allergens:-
The allergens can be classified on the basis
of types of symptoms, which depend on the
shock organs affected by the particular
allergens and its route of entry into the body:
1. Inhalant allergens
2. Ingestant allergens
3. Injectant allergens
4. Contactant allergens
5. Infectant allergens
cynodon dactylon

6. Inhalant allergens
Inhalant allergens are airborne substances as chemicals, causing respiratory disease,
inflammation in the nose and lungs. Inflammation in the nose is manifested by sneezing,
lacrimation, itching and swelling of nose and eyes. The condition is known as sinusitis or
hay fever. Inflammation of lungs is often expressed as asthma. Air pollution, both indoor
and outdoor, plays a significant role in the aggravation of airway disease in the asthmatics
and may contribute to the overall increase in asthma morbidity.
Mouldy Bread Allergic Coughing
Dust Mites

7. Symptoms of allergies to airborne substances are:
• Sneezing often accompanied by a runny or clogged nose
• Coughing and postnasal drip
• Itching eyes, nose and throat.
• Allergic shiner (dark circles under the eyes caused by increased blood flow near the
sinuses)
• The ‘allergic salute’ (in a child, persistent upward rubbing of the nose that causes
mark on the nose)
• Watering eyes, conjunctivitis (an inflammation of the membrane that lines the eye
lids causing red-rimmed, swollen eyes and crusting the eyelids)
As soon as the allergens land on mucous membrane(an inside lining of the nose), a
chain reaction occurs that leads the mast cells in these tissue to release histamine
and other chemicals. These powerful chemical contract certain cells of some small
blood vessels in the nose, which allow fluid to escape causing the nasal passage to
swell resulting in nasal congestions.
The allergens that can cause airborne allergies (inhalant allergens) include pollens,

8. Pollen allergens
Pollens are the tiny, egg-shaped, round, angular, square,
rectangular or otherwise shaped male cells (organ) of flowering
plants. These microscopic, powdery granules are necessary for
plant fertilisation. The average pollen particle size is less than
the width of an average human hair.
These pollens can be further classified into two types:
1. Anemophilous (wind pollinated)
2. Entomophilous (insect pollinated)
Different forms of pollen grains

9. Anemophilous: Anemophilous pollens are usually
small 15–45 m in diameter, light, nonadhesive and relatively
smooth and are produced by plain looking plants, e.g. trees
(oak, walnut); grasses (bermuda grass and timothy) and
weeds (ragweed, plantain).
Entomophilous: Entomophilous pollens are usually
larger in size (up to 200 m in diameter), heavier, adhesive and may
be somewhat spiny. Plants are scented, with coloured flowers
such as clover, hollyhock, honey suckle and rose.
Most common allergic reactions are produced by wind- pollinated
(anemophilous) pollens, because of their light weight and the dry
nature; these pollen grains are carried for long distances.
List of plant or tree producing pollens (allergens):
Alfalfa, almond, apple, acacia, barley, blue grass, canary grass,
cherry, eucalyptus, gladiolus, hazelnut, juniper, mul- berry,
mustard, lemon and related species of citrus.

10. Ingestant Allergens:-
Allergens which are present in food stuff and swallowed are termed ingestant (food
allergy). A food allergy is an immune system response to a food. Once the immune
system decides that a particular food is harmful, it creates specific antibody to it.
The gastrointestinal symptoms are mainly affected by the food allergens, but they also
cause skin rash, puffed lips and tongue, migraine, rhinitis or other symptoms like
severe eczema of hand and feet. The effects of food allergens are not localised to one
organ or area of the body, but it may transfer to other organs by the blood. Thus, an
atopic dermatitis, such as tomato rash, strawberry rash, or that caused by eating
oranges, chocolate or shellfish, is developed by patients.
eczema of hand and feet

11. Some most common food allergens ingested by patients are milk, egg, peanut, tree
nut (walnut, cashew nut, etc.), fish, shellfish, soy, wheat, orange juice, cod liver
oil or other vitamins containing fish liver oils. In addition to the above-mentioned
normal food, there are food additive, which also could be allergic to any individual, viz.
mannitol, sorbitol, polysorbates, malt-dextrins, citrus, bioflavonoids, artificial
preservatives, artificial colours, citrus pectin, talc, soy lecithin, gluten, soy flour, rice
flour, alfalfa, potato starch and gum acacia.
Most satisfactory method of combating food allergens is elimination of the offending
substance from the diet. Dairy milk allergy is a specific immunologic antibody– antigen
reaction due to a lacto-albumin, because heating and boiling alter this protein. Milk allergy
may result in severe dermatitis, recurrent rhinorrhea, bronchitis and asthma. Its antigenicity
can be avoided by the use of commercial milk substitutes that are prepared from soya bean
isolates.
Shellfish
Atlantic Cod
Cod Liver OIL

12. Injectant Allergens:
Injectant allergens cause symptoms similar to those
of the antibiotics, e.g. penicillin, cephalosporin and
semisynthetic penicillin, etc. Itching of the palms of
the hands and the soles of the feet, erythema and
peeling of the skin are char- acteristic. In severe
cases anaphylactic shock may occur.
The natural sources of injectable allergens are
produced by the sting of bees, hornets and wasps.
The allergens injected by the stings of such insects
can induce severe local and constitutional reactions
sometimes causing death.
In addition to penicillin products, other injectable that
may cause allergies are liver extract, antitoxins and
the glandular products.
bumble bee
honey bee Wasp
Sting of Bee

13. Contactant Allergens:-
A number of plants and their products have been identified as the
causes of contact allergies. The plant most responsible for contact
dermatitis in North America belongs to the Ancardiaceae family;
primarily the genus Toxicodendron (Rhus) and includes poison
ivy, oak and sumac. The allergen component of these plants, called
urushiols (a phenolic compound) are found in the oleoresin fraction
and are derivatives of pentadecylcatechol or heptadecylcatechol.
Many plants of compositae family, which include the ragweeds, also
cause contact dermatitis and the allergens responsible had been
identified as Sesquiterpenoids lactone.
Other plants species, which can give rise to contact allergic
reactions are Ruta graveolens, asparagus, ornamental ‘dumb cane’
(Dieffenbachia seguine), buck wheat, butter cups, catalpa leaves,
chrysanthemums, ginkgo leaves, lobelia, marigolds, may-apple,
osage orange, flowering spurge, snow on the mountains and smart
weeds.
Butter Cup Flower/Ranunculus
Ornamental Dumb Cane

14. Infectant
Allergens:-
Allergy caused by the metabolic product of living
microorganism in the human body, such as the
continual presence of certain types of bacteria,
protozoas, moulds, helminthes and other parasites
in the body of human being that are responsible for
chronic infection for which patients are not aware.
Often the metabolic product of their growth causes
some patient sensitized and the patient may exhibit
allergic symptoms, which does not response
positively to routine skin test for inhalant allergens.
In such patients, bacterial metabolic wastes are
considered to be infectant allergens.
The continuous presence of growth products and
meta- bolic waste of parasitic organism such as
hookworms, tape worms, pinworms, threadworms
and dermatophytes are referred as infectant
allergens.
Roundworms
Hookworm Infected Human

15. Fungi And Mold Allergy:
• Mold is a fungus that grows in the form of
multicellular filaments called hyphae, which makes
spores rather than seeds.
• Some food items most commonly associated with
fungus includes mushroom, soy sauce, bread, dairy
product etc.
• It results in the discolouration and fuzzy appearance
especially on food.
• When people inhale the spores they get allergic
symptoms.
• Common health problem created by fungi and
moulds are allergic asthma, allergic rhinitis,
dermatitis, hypersensitivity pneumonitis etc.
Fig.:- Some food associated
with FUNGI

16. • There are many type of moulds, only a few dozen
cause allergic reactions are: Altemaria, Cladosporium,
Aspergillus, Penicillium, Mucor, Epicoccm, Rhizopus.
• Mycotoxins are secondary metabolites of fungi which
can induce acute as well as chronic toxic effects (i.e.,
carcinogenicity, mutagenicity, teratogenicity) in animals
and man.
• Mould grows in rotten logs and fallen leaves, in
compost piles and on grasses and grains. Unlike
pollens, moulds do not die with the first killing frost.
Most outdoor moulds become dormant during the
winter.
• Indoors grown in damp areas.

17. Prevention
• Avoid contact with spores, wear mask when
working in field.
• Reduce the humidity indoors to prevent
fungi from growing.
• Take medication if necessary e.g. cetrizine,
chlorpromazine, chlorpheniramine etc.
• Maintain Cleanliness as much as possible