Allergy

IgE antibody

Type 1 hypersensitivity and IgE-mediated

IgE binds to Fc receptors on mast cells Allergen crosslinks with IgE + basophils + eosinophils This causes entry of Ca<strong>2+</strong> ions Mast cells undergo degranulation (of histamine) + release of inflammation mediators to cause: • permeability • chemotaxis • mucus • oedema

Inflammation of the inside of the nose caused by an allergen

Perennial = house dust mite + animal hair/FUR Seasonal = hay fever - pollen Occupational = latex Associated with atopy (genetic predisposition)

Nasal itching Sneezing Rhinorrhoea - runny nose Conjunctival - itchy red eye (worsened by irritants)

Histamine - acts on H1 receptors

Avoid pollen in spring by staying indoors or wearing glasses Avoid dust mites by: • vacuuming • wooden floors over carpets • wash bed clothes @ 60 degrees • freeze pillows

A drug that treats allergic rhinitis It removes rhinorrhoea, itching, conjunctivitis + sneezing but not nasal obstruction Act as H1 antagonist Penetrate BBB (blood-brain barrier) Have anti-muscarinic effects (promethazine) Not ideal, effects of alcohol enhanced

Chlorphenamine e.g. piriton (or syrup for children over 1 year) Alimenazine* e.g. trimeprazine Promethazine* e.g. phenergen * = more so

Loratadine (clarityn) - 1st CHOICE Acrivastine (benadryl) - have to be taken tds (not ods) Cetrizine (zirtek) Fexofenadine (telfast) - POM

Azelastine (rhinolast) Rapid onset Effective but not for eye symptoms Azelastine in eye drop formulation for allergic conjunctivitis = rapid relief Also lodoxamine as eye drops

Beclometasone Budesonide Fluticasone Triamcinolone Anti-inflammatory = Reduce cytokines and chemokines which reduce recruitment of immune cells in epithelial mucosa

Mast cell stabiliser - Inhibits mast cell degranulation e.g. sodium cromoglicate + medocromil sodium Nasal + eye Weak effect Many side effects Used for seasonal disease Up to 4-6 times daily Eye drops - most effective for conjunctival symptoms

Montelukast Less effective than nasal steroids Licensed for seasonal allergic rhinitis with asthma

Blocked or stuffy nose e.g. allergic rhinitis or common cold Excess mucus production Histamine causes increased blood flow leading to nasal tissue swelling (oedema) which is caused by: • colds, rhinitis, sinusitis Decongestants cause nasal vasoconstriction to reduce nasal tissue swelling + mucus flow alpha1 adrenoceptors cause vasoconstriction

Symptomatic relief - reduce feeling of congestion Both topical + systemic decongestants act on alpha-adrenoceptors Topical ‘nasal’ treatment: • phenylepherine (alpha1) • xylometazoline/oxymetazoline (alpha2) Alpha-adrenoceptor agonist cause vasoconstriction Reverse vasodilatation Reduce flow of mucus Act locally Rebound congestion - use for < 7 days

e.g. phenylepherine (alpha1-adrenoceptor = selective)

Desensitisation towards an allergen Could be effective for hayfever - when allergen is identified _ conventional treatment has failed Appropriate for wasp + bee venom sting

Grazax® contains a grass pollen allergen. By taking many small doses of Grazax you are able to build up a tolerance to grass pollen. This reduces the symptoms of your allergic reaction. Take 4 months before pollen season and then daily Uncertain if effective

A serious, life-threatening allergic reaction Can cause more than one of the following: • angioedema = swelling of lower skin • wheezing • itching • hypotension

Oxygen Adrenaline - increase CO2 + bronchodilation Salbutamol = wheezing Chlorphenamine (antihistamine) - IV/IM Hydrocortisone - IV Shock boxes EpiPens Medic alert bracelet

People who have been prescribed an adrenaline auto-injector because of the risk of anaphylaxis should carry two with them at all times for emergency, on-the-spot use. After every use of an adrenaline auto-injector, an ambulance should be called (even if symptoms are improving), the individual should lie down with their legs raised and, if at all possible, should not be left alone