Lecture 15: Minor Ailments & Responding to Symptoms in Community Pharmacy | Allergy & Hay Fever

What is allergy?

• Immune system reacting to a normally harmless substance

• Hypersensitivity disorder

• Allergen - a substance that triggers allergy

• Risk factors - heredity, gender, race and age

• Environmental factors - pollution allergen levels aand dietary changes

Atopy:

• Genetic predisposition to make IgE antibodies in response to allergen exposure

• Atopic disorders most commonly affect the nose, eyes, skin & lungs

• Allergic rhinitis (e.g., hay fever), allergic asthma, atopic dermatitis (eczema) - most common manifestations of atopy

Examples

Typical Allergens

• Proteins e.g. foreign serum, vaccines

• Plant pollens e.g. rye grass, ragweed, timothy grass

• Drugs e.g. penicillin

• Foods e.g. nuts, seafood

• Insect products e.g. bee venom

• Mold spores

Allergic reactions

• Allergens enters the body > activates B cells (plasma cells) to produce immunoglobulin (IgE) > antibodies to the allergen: released into blood stream, bind mast cells which become primed

Future exposure to the allergen:

• Primed mast cell degranulation

• Histamine release into local tissue

• Type I (immediate) hypersensitivity reaction

Allergy vs Sensitisation

Sensitisation

• Initial ‘learning’ phase of an allergic response (primes immune system to react to a specific allergen)

• Occurs before the developement of Type I hypersensitivity reaction

• Asymptomatic or mild reaction

Allergic reaction

• Repeated exposure - more serious reaction

• Limited exposure to very small amount of allergen can trigger a severe ‘full-blown’ reaction

• Type I hypersensitivity reaction:

  • Earlu phase (seconds/minutes < 1 hour) - rapid degranulation releasing histamines, leukotrienes, prostaglandines and other inflammatory mediators. Severe cases ( anaphulaxis)

  • Late phase (4-12 hours) - inflammation sustained by recruitment of eosinphils, neutrophils, basophils, moncytes and Th2 cells

Allergic symptoms

Type I hypersensitivity:

• Early phase symptoms:

  • Vasodilation > redness ad swelling

  • Increased muscular vascular permeability > fluid leakage, wheals

  • Smooth muscle contraction > bronchoconstriction

  • Mucus secretion > runny nose, congestion

• Late phase symptoms:

  • Examples: prolonged symptoms like asthma, dermatitis, chronic rhinitis

Actions of histamine on H1 receptors

• Local hormone (autocoid)

• Blood vessels - dilatation + capillary increased

• Smooth muscle - contraction

• Stimulation of sensory nerves

• Increased gland secretion

• Anaphylactic shock - circulation collapse & bronchoconstriction - largely mediated by histamine

Prevention

• Allergen avoidance - good history taking, read labels

• Serious allergic reaction - medical ID tag, carry emergency medicines

Allergic Rhinitis

• Inflammation of the inside of the nose resulting in sneezing attacks & nasal discharge or blockage

• Can have profound impact on quality of life, work and education

• Long-term problems due to inflammation

  • Nasal polyps

  • Sinusitis

  • Middle ear infections

Allergic Rhinitis

1. Seasonal (hay fever)

• Usually outdoor allergens, pollens, moulds

• Symptoms > 1hr a day

2. Perennial

• Indoor allergens e.g. house dust mites, moulds, animals

• Symptoms year-round constant

3. Occupational

• Allergens at work e.g. dust from eood, flour, latex

Management

Non-pharmacological

• Allergen avoidance

• Hay fever

  • Monitor pollen counts

  • Keeps windown closed

• Persistent allergic rhinitis

  • Exclude pets from certain living areas

  • Acaricidal sprays & bedroom cleaning regimens

Pharmacological

• H1 receptor antagonists

• Mast cell stabilisers

• Intranasal corticosteroids

• Intranasal decongestants

Antihistamines

• H1 receptor antagonists

• Reversible binding to the H1 receptor

• More efective at preventing than reversing symptoms

• Block triple response of Lewis

• Partially prevent hypotensive effect

• No effect on gastric secretions

Antihistamine examples

• Usually first line

• Oral (systemic action)

• 2nd generation preferable to 1st 

• Some available as solid & liquid dosage forms licensed for children & adults

• GSL, POM & P

• Add eye drops and/pr intranasal corticosteriod sprays nasal, if eye or nasal symptoms persist

Eye drops

• Mast cel stabilisers

• Prevent histamine release - need to be used regularly while exposed

• Sodium cromoglicate

• For itchy & runny eyes

• P medicine

Intranasal Corticosteriods

• 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 reduces side effects compared to oral dosage forms

• Several days to obtain effect & several weeks for full effect

• Can be used with oral antihistamines

• GSL, P & POM dependent on number of unit doses

• GSL, P only licensed for adult only

• Under 18 years old - POM

Local Vasoconstrictors ‘nasal decongestants’

• Phenylephrine (works within ~15 minutes, short-acting, lasts up to 4 hours), oxymetazoline, xylometazoline (works within a few minutes, lasts up to 8 hours)

• Mimic noradrenaline, 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)

• Not recommended for use with antihistamines

Rhinitis medicamentosa

• Rebound congestion following vasoconstriction (avoid by 7-day max. use limit)

• 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

Allergic rhinitis or cold?

• Family history of atopy (asthma, eczema, hay fever)

• Clinical symptoms & when they get worse

When to refer

Where allergic rhinitis symptoms aren’t controlled despite antihistamine, eye drops & nasal corticosteriod:

• Sleep disruption

• Impairing ability to work/study

Nasal obstruction fails to clear

• Symptoms only appearing on 1 side

• A blocked nose with no other symptoms

Orbital cellulitis - infected eyelids causeing swelling, pain, photophobia, recurrent nosebleeds (epistaxis)