Minor Ailments - Allergy & hay fever Flashcards
1
Q
What is allergy?
A
- Immune system reacting to a normally harmless substance
- Allergen – a substance that triggers allergy
- Some people are more prone to allergy than others= have genetic disposition
- Risk factors:
Heredity, gender, race, & age - Environmental factors
- Early exposure might be protective
- Environmental pollution, allergen levels & dietary changes
- Allergic disorders – asthma, eczema, hay fever= ATOPIC TRAID @ hugher risk i.e if s/o has asthma which is triggered by allergens they have a higher risk of ecezema & hayfever
2
Q
Mechanism
A
- First-time exposure = mild reaction
- Repeated exposure = more serious reaction ; of primed mast cells
- A person is sensitized = limited exposure to a very small amount of allergen can trigger a severe reaction ; of primed mast cells
- Timeframe - seconds or minutes after exposure to the allergen, but some can be prolonged (ingestion). Rare after 24 hours.
- IgE mediated reactions = Type I (immediate) hypersensitivity
Atopy= atopic triad: - Genetic predisposition to make IgE antibodies in response to allergen exposure
- Allergic rhinitis, allergic asthma, atopic dermatitis are the most common manifestation of atopy
2
Q
What sites can be affected
A
2
Q
Allergic reactions
A
- Affects allergy prone individuals
1. Allergen such as pollen enters body
(skin, inhalation, ingestion, injection)
2. Activates B cells (plasma cells) to produce Immunoglobulin ( spedific to the allergen) E (IgE) Antibodies to the allergen - Released into blood stream
- Bind mast cells (abundant in the mucosa of the respiratory,
gastrointestinal tracts and in the skin) which then become primed
3. Future exposure to the allergen - Primed mast cells degranulation
- Histamine release into local tissue
- If they meet the allergen again it will release those cytokines into the blood stream
4. Allergy symptoms
3
Q
Actions of Histamine on H1 Receptors
A
- Causes allergic reactions
- Local hormone (autocoid) auto = produced by the cell
autocoid = local reaction - Blood vessels – dilatation + capillary permeability increased (oedema) = Causes blood vessels to dilate & makes them become leaky leading to oedema and skin itch and anaphylactic shock
- Smooth muscle – contraction in lungs = broncho constriction = can’t breathe
- Skin – itch = senosry nerve endings
- Anaphylactic shock
- circulatory collapse &
bronchoconstriction – largely
mediated by histamine
3
Q
Allergens – Type 1 hypersensitivity causes
A
- Proteins (e.g., foreign serum, vaccines)
- Plant pollens (e.g., rye grass, ragweed, timothy grass, birch trees)
- Drugs (e.g., penicillin, sulfonamide(old school antiobiotic caused people skin to drop off) - drugs, local anaesthetics, salicylate-drugs= i.e aspirin )
- Foods (e.g., nuts, seafood, eggs, peas, beans, milk)
- Insect products (e.g., bee venom, wasp venom, ant venom, dust mites, cockroach calyx, animal hair, animal dander)
- Mold spores
4
Q
Actions of Histamine on the skin - Triple response of Lewis
A
Firm scratch of skin
1- red line (15s)= Capillary dilation
2- flare around line (45s) =Arteriolar dilation
3- Wheal (3 mins)=Exudation of fluid
- Caused by histamine
4
Q
Symptoms of allergy
A
- Sneezing
- Wheezing
- Sinus pain
- Runny nose (rhinorrhoea)
- Cough
- Vomiting & diarrhoea
- Urticaria (hives)
5
Q
Prevention
A
- Best way = to avoid (even for milder cases):
to narrow down what the allergen is good history taking is needed & read labels - Serious allergic reactions:
Medical ID tag – Wear a tag/bracelet
carry emergency medicines (e.g., im adrenaline autoinjector pens= reverse effects of histamine release) - Histamine constrict bronchioles adrenaline will relax them
- histamine dilates blood vessels adrenaline constricts them
6
Q
Allergic Rhinitis
A
- Inflammation of the inside of the nose resulting in sneezing attacks & nasal discharge or blockage
- 1 in 5 people in the uk are affected
- ## can have a profound impact on quality of life, work and education
7
Q
allergic rhinitis, Long-term problems due to
inflammation
A
Continous inflammation can cause:
* Nasal polyps (benign sacs of fluid in the nasal passages and sinuses)
* Sinusitis – infection – caused by swelling and inflammation preventing mucus drainage from the sinuses
* Middle ear infection
8
Q
Symptoms of allergic rhinitis
A
w/ frequent bouts of sneezing =
- nasal congestion
- red, ithcy swollen eyes
can persist for weeks affecting:
- concentration
- sleep
- atendace @ work or school
8
Q
what are the 3 types of allergic rhinitis
A
1. Seasonal (hay fever)
* usually outdoor allergens, pollen, moulds
(Tree pollen: February to April
Grass pollen: May to August
Fungal spores: Sept to October)
* Symptoms > 1hr a day (usually less than 4 weeks)
2. Perennial
* indoor allergens e.g., house dust mites, moulds,
animal (pets) dander (skin flakes)
* Symptoms year-round constant – perennial (> 4
weeks)
3. Occupational
* allergens at work e.g., dust from wood, flour, latex
* s/t in the work in environment that causing s/o to have a reaction
9
Q
Antihistamines
A
- H1 receptor antagonists (antihistamines)
- Reversible binding to the H1 receptor
- More effective at preventing than reversing symptoms
- Block triple response of Lewis
- Partially prevent hypotensive effect
- No effect on gastric secretions (H2 receptors antagonists needed for that)
- Competes w/ the histamine in the system for the receptor
- Bocks what histamine does
- No effect on gastric effects
10
Q
Management- Non-Pharmacological
A
- Allergen avoidance= best
- hay fever:
- Monitor pollen counts
- Keep windows closed/stay indoors
- Wrap-around sunglasses= stops pollen getting in eyes
- Vaseline around nose to stop it form getting into nasal passages
- Persistent allergic rhinitis:
- Exclude pets from certain living areas
- Acaricidal sprays & bedroom cleaning regimens
- Minimising carpets & soft furnishings, allergen-impermeable fabric bedding
- Self-care treatments such as saline nasal washes may (limited evidence)
11
Q
Management- Pharmacological
A
- H1 receptor antagonists (antihistamines)
- Mast cell stabilisers
- Intranasal corticosteroids
- Intranasal decongestants (local vasoconstrictors)
12
Q
Antihistamines
A
12
Q
1st gen Antihistamines
A
Chlorphenamine
Diphenhydramine
Promethazine
(piriton
benedryl)
13
Q
2nd gen Antihistamines
A
Cetirizine (& levocetirizine)
Loratadine (& desloratadine)
Fexofenadine
Acrivastine
(zirtek, clarityn)
14
Q
Antihistamines
A
- Usually first-line= usually 2nd gen & loratadine = least sedative
- Oral (systemic action)
- 2nd generation preferable to 1st generation= 2nd gen taken 1 oe x2 daily while 1st gen = 3or 4x daily
- ↓Side effects
- ↓Frequency of dosing
- Some available as solid & liquid dosage forms licensed for children & adults
- GSL, P & POM= depends on pack size
- Add eye drops and/or intranasal corticosteroid sprays nasal or eye symptoms persist
14
Q
Mast cell stabilisers
A
- Prevent histamine release
- need to be used regularly while exposed
- Sodium cromoglicate eye drops
- For itchy and runny eyes
- Four times daily = CON
- Sterile, isotonic with tears
- Contains preservative (avoid with contact lenses)= CON
- P medicine
- If oral products don’t work
15
Q
Intranasal Corticosteroids
A
- can be offered OTC
- Beclometasone, budesonide, fluticasone, triamcinolone, mometasone
- Most effective treatment for allergic rhinitis
- Reduce local inflammatory response
- Improve rhinorrhea, itchiness, sneezing, congestion
- Systemic absorption is minimal (local action)
- Advantage decrease side effects compared to oral dosage forms
- Several days to obtain effect & several weeks for full effect= good for long time use as it takes time to have full effect
- Can be used with antihistamines
- GSL, P & POM dependent on number of unit doses
- GSL, P only licensed for adult only
- Under 18 years old - POM
15
Q
Local vasoconstrictors “nasal decongestants”
A
- short term use
- Phenylephrine (works within ~15 minutes, short-acting, lasts up to 4 hours),
oxymetazolone, xylometazolone (works within a few minutes, lasts up to 8 hours) - Mimic noradrenaline ( SNS), bind alpha-adrenoreceptors to constrict dilated arterioles in the
nasal mucosa & reduce airway resistance - Nasal drops or spray
- Rapid action
- Reduced systemic effects (compared to oral decongestants)
- Rhinitis medicamentosa
- Rebound congestion following vasoconstriction (don’t use fr more than 7 days= blood vessels don’t react anymore= desensitized)
- Pathophysiology unknown, possibly due to decreased local production of noradrenaline
- Only occurs with local vasoconstrictors
- Recovery reported to take up to a year in cases of long-term overuse report
- Not recommended for use with antihistamines
16
Q
when to refer?
A
- Where allergic rhinitis symptoms are not controlled despite antihistamine & eye drops & intranasal corticosteroid:
- Sleep disruption
- Impairing ability to work/study
- Nasal obstruction that fails to clear (possible polyp):
- symptoms only appearing on one side
- a blocked nose with no other symptoms
- Orbital cellulitis – infected eyelids causing swelling
- Pain
- Photophobia= sensitivity to light
- Recurrent nosebleeds (epistaxis)
16
Q
Differential diagnosis
A
- is it a cold or allergic rhinitis?
- Family history of atopy (asthmas, eczema, hay fever)
- Do tehy have the genetic predisposition
- Clinical symptoms & when they get worse
- Seasonal variation vs perennial
- Colds don’t usually last over in 2 weeks
- Allergic rhinitis symptoms occur rapidly upon exposure
- Cold may typically have congestion or a runny nose (rhinorrhoea), the mucus is (usually) more viscous and sneezing bouts are less likely
- Allergic rhinitis, rhinorrhoea profuse & watery, may stimulate several episodes of sneezing in quick succession
- Coughs and sore throats can occur with allergic rhinitis but more common with a cold
- Nasal itch & eye symptoms rare with a cold but common in allergic rhinitis
- Loss of smell not unusual with a cold, but unusual in allergic rhinitis
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