L22 Seasonal respiratory allergies

Allergic Rhinitis is hay fever, caused by seasonal allergens like ❌, and perennial allergens like ❌.
Common symptoms include a runny, stuffy ❌, sneezing, cough, wheezing, and itchy, red, watery ❌.

The pathology of hay fever has 2 key stages, ❌ and re-exposure causing inflammation.
Upon re-exposure to an allergen, ❌ cells in the nasal ❌ primed with IgE antibodies release ❌, leukotrienes, and prostaglandins. ❌ cause the infiltration of lots of ❌ immune cells. These release mediators. The blood vessels become more porous, ❌ and emptying easier. Histamines bind to blood vessels, ❌ cells and nerves.

Early-phase symptoms (minutes):
- ❌
- nasal ❌ and congestion
- rhinorrhoea (❌ nose)
Late-phase symptoms (6-12 hr):
- nasal ❌
- nasal hyperactivity

Therapy options for allergic rhinitis are drugs for symptomatic relief, and to avoid triggers. Dosage forms are:
• ❌ tablets
• ❌ sprays
• ❌ drops
Drugs can:
- Prevent release (❌)
- Prevent inflammation (❌)
- Block action (❌)

H1 antihistamines are ❌ and not receptor antagonists.
Therefore they have no effect on histamine ❌ from storage ❌ and are more effective if given ❌ histamine release occurs. H1 antihistamines can decrease the itch, decrease vascular ❌, decrease ❌ presentation and pro-inflammatory cytokines, increase mast cell ❌ and decrease ❌ release.

First generation H1 antihistamines have low ❌ selectivity and high ❌ permeability. They take ❌ hours to onset of action, and last ❌ hours. They are taken ❌. Their side effects can include sedation, dry ❌, urinary ❌, increased appetite, postural ❌ or dizziness, and possibly ventricular arrythmias.
Second generation antihistamines have ❌ H1 selectivity and ❌ BBB permeability, therefore side effects are uncommon. They take ❌ hours to onset of action, and the majority of them are dosed ❌ daily, lasting for 24 hours.

Corticosteroid nasal sprays act primarily during the ❌ phase and are good for ❌ term management. For allergic rhinitis there is no linear association between glucocorticoid ❌ and clinical ❌, meaning we can use a low potency glucocorticoid effectively.
Since it is intranasally sprayed, systemic absorption would be negligible and would be expected to pose ❌ side effects. But those are:
• Dryness, stinging, burning, and ❌
• Nasal mucosal atrophy, with ❌ topical steroid use

Intranasal decongestants are ❌ drugs like xylometazoline & oxymetazoline. They have a ❌ onset of action though are used ❌ duration, as you risk ❌ congestion. The drugs act on ❌ in the nasal blood vessels, fixing ❌, but not congestion.