Transcript What Are Allergies?

Clinical Pharmacy in
Allergology
Allergies
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Allergic Rhinitis ('hay fever')
Asthma
Chronic Sinusitis
Eczema (Atopic Dermatitis)
Chronic Hives & Angioedema (swelling)
Food Allergies
Allergies to Insect Stings
Contact Dermatitis
Less common conditions including
anaphylaxis, drug allergies and immune
deficiencies.
What Are Allergies?
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Allergies are a reaction by the body's
immune system to harmless
substances that it sees as
harmful. The allergy causing
substances are called allergens. It is
as if the immune system is overlyactive in response to otherwise
innocuous substances.
TERMS
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Allergen—A substance that provokes an
allergic response.
Anaphylaxis—Increased sensitivity caused by
previous exposure to an allergen that can result
in blood vessel dilation (swelling) and smooth
muscle contraction. Anaphylaxis can result in
sharp blood pressure drops and difficulty
breathing.
Antibody—A specific protein produced by the
immune system in response to a specific
foreign protein or particle called an antigen.
Antigen—A foreign protein to which the body
reacts by making antibodies.
Routes:
Allergens enter the body through
the airways, the skin, the gastrointestinal tract, and the
circulatory system
SYMPTOMS
Airborne allergens cause the sneezing, runny nose,
and itchy, bloodshot eyes of hay fever (allergic rhinitis).
Airborne allergens can also affect the lining of the
lungs, causing asthma, or the conjunctiva of the eyes,
causing conjunctivitis (pink eye). Exposure to cockroach
allergans have been associated with the development
of asthma. Airborne allergans from household
pets are another common source of environmental
exposure.
SYMPTOMS
Allergens in food can cause itching and swelling of the
lips and throat, cramps, and diarrhea. When absorbed
into the bloodstream, they may cause hives (urticaria)
or more severe reactions involving recurrent,
noninflammatory swelling of the skin, mucous
membranes, organs, and brain (angioedema). Some
food allergens may cause anaphylaxis, a potentially lifethreatening condition marked by tissue swelling,
airwayconstriction, and drop in blood pressure. Allergies
to foods such cow’s milk, eggs, nuts, fish, and legumes
(peanuts and soybeans) are common. Allergies to fruits
and vegetables may also occur.
SYMPTOMS
In contact with the skin, allergens can cause reddening,
itching, and blistering, called contact dermatitis.
Skin reactions can also occur from allergens introduced
through the airways or gastrointestinal tract.
This type of reaction is known as atopic dermatitis.
Dermatitis may arise from an allergic response (such
as from poison ivy), or exposure to an irritant causing
nonimmune damage to skin cells (such as soap, cold,
and chemical agents).
SYMPTOMS
Injection of allergens, from insect bites
and stings or drug administration, can
introduce allergens directly into the
circulation, where they may cause systemwide responses (including anaphylaxis),
as well as the local ones of swelling and
irritation at the injection site.
The following types of drugs commonly
cause allergic reactions:
• penicillin or other antibiotics
• flu vaccines
• tetanus toxoid vaccine
• gamma globulin
SYMPTOMS (cont’d)
Symptoms depend on the specific type of allergic
reaction. Allergic rhinitis is characterized by an itchy,
runny nose, often with a scratchy or irritated throat due
to post-nasal drip. Inflammation of the thin membrane
covering the eye (allergic conjunctivitis) causes redness,
irritation, and increased tearing in the eyes. Asthma causes
wheezing, coughing, and shortness of breath.
SYMPTOMS (cont’d)
Symptoms of food allergies depend on the tissues most
sensitive to the allergen and whether the allergen spread
systemically by the circulatory system. Gastrointestinal
symptoms may include swelling and tingling in the lips,
tongue, palate or throat; nausea; cramping; diarrhea; and
gas. Contact dermatitis is marked by reddened, itchy,
weepy skin blisters, and an eczema that is slow to heal. It
sometimes has a characteritic man-made pattern, such as
a glove allergy with clear demarkation on the hands,
wrist, and arms where the gloves are worn, or on the
earlobes by wearing earrings.
Skin reactions
Skin reactions
include the raised, reddened, and itchy patches called
hives that characteristically blanch with pressure and
resolve within twenty-four hours. A deeper and more
extensive skin reaction, involving more extensive fluid
collection and pain, is called angioedema. This usually
occurs on the extremities, fingers, toes, and parts of the
head,neck,and face.
Anaphylaxis
Anaphylaxis is marked by airway constriction, blood
pressure drop, widespread tissue swelling, heart rhythm
abnormalities, and in some cases, loss of
consciousness. Other syptoms may include, dizziness,
weakness, seizures, coughing,flushing, or cramping.
The symptoms may begin within five minutes after
exposure to the allergan up to one hour or more later.
Mast cells in the tissues and basophils in the blood
release mediators that give rise to the clinical symptoms
of this IgE-mediated hypersensitivity reaction. Commonly,
this is associated with allergies to medications, foods,
and insect venoms.
Anaphylaxis
In some individuals, anaphylaxis can
occur with exercise, plasma exchange,
hemodialysis, reaction to insulin,
radocontrast media used in certain types
of medical tests. and rarely during the
administration of local anesthetics.
The allergic response
Treatment
Avoiding allergens is the first line of defense to reduce
the possibility of an allergic attack.
Complete environmental control is often difficult to
accomplish, hence therapuetic interventions may
become necessary. A large number of prescription and
over-the-counter drugs are available for treatment of
immediate hypersensitivity reactions. Most of these
work by decreasing the ability of histamine to provoke
symptoms. Other drugs counteract the effects of histamine
by stimulating other systems or reducing immune
responses in general.
Treatment
ANTIHISTAMINES block the histamine
receptors on nasal tissue, decreasing the
effect of histamine released by mast cells.
They may be used after symptoms appear,
though they may be even more effective
when used preventively, before symptoms
appear. Antihistamines are help reduce
sneezing, itching, and rhinorrhea.
Treatment
I generation antihistamines side effect
Drowsiness
dry mouth,
tachycardia,
blurred vision,
constipation,
lower the threshold for seizures.
diphenhydramine (Benadryl and generics)
chlorpheniramine (Chlor-trimeton and generics)
brompheniramine (Dimetane and generics)
clemastine (Tavist and generics)
These medicatios care should be taken when operating motor vehicles
Treatment
Newer antihistamines that do not cause
drowsiness or pass the blood-brain barrier
are available by prescription and include the
following:
• loratidine (Claritin)
• fexofenadine (Allegra)
Treatment
MAST CELL STABILIZERS
Cromolyn sodium prevents the release of mast cell
granules, thereby preventing the release of
histamine and other chemicals contained in
them. It acts as a preventive treatment if it is
begun several weeks before the onset of the
allergy season.
It can also be used for year round allergy
prevention. Cromolyn sodium is available as a
nasal spray for allergic rhinitis and in aerosol (a
suspension of particles in gas) form for asthma.
Treatment
LEUKOTRIENE MODIFIERS
These medications are useful for individuals
with aspirin sensitivity,sinusitis,
poliposis, urticaria. Examples include
zafirlukast (Accolate), montelukast
(Singulair), and zileuton (Zyflo).
When zileuton is used, care must be taken to measure liver
enzymes.
ALLERGIC RHINITIS
Allergic rhinitis, more commonly referred to as hay
fever, is an inflammation of the nasal passages caused by
allergic reaction to airborne substances.
Allergic rhinitis (AR) is the most common allergic
condition and one of the most common of all minor
afflictions.
There are two types of allergic rhinitis: seasonal and
perennial. Seasonal AR occurs in the spring, summer,
and early fall, when airborne plant pollens are at their
highest levels. In fact, the term hay fever is really a
misnomer, since allergy to grass pollen is only one cause
of symptoms for most people. Perennial AR occurs all
year and is usually caused by home or workplace
airborne pollutants. A person can be affected by one or
both types.
Symptoms of seasonal AR are worst after being
outdoors, while symptoms of perennial AR are worst
after spending time indoors.
ALLERGIC RHINITIS. Symptoms
Inflammation causes
itching, sneezing, runny nose, redness, and
tenderness. Sinus swelling can constrict the
eustachian tube that connects the inner ear to
the throat, causing a congested feeling and “ear
popping.”
The drip of mucus from the sinuses down the
back of the throat, combined with increased
sensitivity, can also lead to throat irritation and
redness. AR usually also causes redness,
itching, and watery eyes. Fatigue and
headache are also common.
ALLERGIC RHINITIS. Treatment
Avoidance of the allergens is the best treatment, but
this is often not possible. When it is not possible to avoid
one or more allergens, there are two major forms of
medical treatment, drugs and immunotherapy.
DRUGS
ANTIHISTAMINES. Antihistamines block the histamine
receptors on nasal tissue, decreasing the effect of
histamine release by mast cells. They may be used after
symptoms appear, though they may be even more effective
when used preventively, before symptoms appear. A
wide variety of antihistamines are available.
Treatment of anaphylaxis
The emergency condition of anaphylaxis is treated with
injection of adrenaline (epinephrine).
Paticular care should be taken to assess the affected
individual’s airway status, and he or she should be placed
in a recumbent pose and vital signs determined.
If a reaction resulted from insect sting or an injection, a
tourniquet may need to be placed proximal to the area
where the agent penetrated the skin. This should then be
released at intervals of ten minutes at a time, for one to
two minutes duration.
Oxygen may be given, as well as intravenous
replacement fluids.
Antihistamines may be used for skin rash, and
aminophylline for bronchial constriction. If the upper
airway is obstructed, placement of a breathing tube or
tracheostomy tube may be needed.
Immunologic Reactions to Drugs &
Drug Allergy
Immediate (Type I) Drug Allergy,
Autoimmune (Type II) Reactions to Drugs,
Serum Sickness & Vasculitic (Type III)
Reactions.
Drug hypersensitivity is defined as an immunemediated response to a drug agent in a sensitized
patient. Drug allergy is restricted specifically to a
reaction mediated by IgE.
Immune-mediated reactions account for 5
to 10 percent of all drug reactions and
constitute true drug hypersensitivity, with
IgE-mediated drug allergies falling into this
category.
Type I reactions (IgE-mediated); Type II
reactions (cytotoxic); Type III reactions
(immune complex); and Type IV reactions
(delayed, cell-mediated).