Hayfever

HEYFEVER

Seasonal allergic rhinitis and/or conjunctivitis, more commonly known as hayfever, are allergic hypersensitivity reactions in the nasal mucosa and the conjunctiva of the eye associated with the presence of pollens in the atmosphere in the summer months.

Causes

■■ Hayfever is caused by exposure to pollen or other allergens that only occur at certain times of year. The most common causes are:

–– tree pollens in spring

–– grass pollen in summer

–– mugwort and chrysanthemum pollen and fungal spores in autumn.

■■ Symptoms are the result of a type I allergic reaction in which initial exposure of a sensitive individual to an antigen results in the production of antigenspecific immunoglobulin E (IgE). IgE attaches to mast cells and basophils, which become sensitive to further antigenic material. On further exposure the antigen binds to IgE, causing degranulation of the mast cells and release of chemical mediators, including histamine, leukotrienes and prostaglandins, which produce an inflammatory response. Prolonged exposure to the allergen may result in a sustained response, causing nasal congestion.

Epidemiology

■■ Hayfever is estimated to affect 10–15% of the UK population, and the incidence appears to be rising.

■■ Up to 10% of children and 20–30% of adolescents are thought to suffer. Incidence peaks in the early teens and then diminishes. About two-thirds of adult sufferers are under 30 years old.

■■ Heredity may play a role, and children whose parents suffer from hayfever have

a high chance of suffering themselves.

Signs and symptoms

Nasal symptoms

The development of nasal symptoms over time is described in terms of early and late phases.

Early-phase nasal symptoms

■■ Rhinorrhoea (nasal discharge): discharge is clear and watery, and frequent blowing and wiping can make the nose sore, sometimes leading to infections.

■■ Sneezing: begins within 60 seconds of inhalation of allergen and can result in long bouts of repeated sneezing, which is disruptive and distressing.

■■ Nasal pruritus (itching): may be continuous or intermittent, and is extremely unpleasant and irritating.

■■ Some sufferers also experience an itching sensation in the roof of the mouth.

Late-phase nasal symptoms

■■ Nasal congestion, usually developing after some days of exposure to allergen, when the blood vessels in the nose become dilated. Congestion may be uni- or bilateral, and may shift from one nostril to the other every few hours. Mouthbreathing may result, which can lead to a dry mouth and bad breath, disrupted sleep and anosmia (loss of sense of smell).

■■ Nasal congestion may cause frontal or sinus headaches and give rise to secondary infections such as sinusitis.

■■ The eustachian tubes may become blocked with mucus and infected, and otitis media may result.

■■ In some cases a dark or bluish swelling, like a black eye, develops around the eyes, caused by impaired nasal venous outflow.

Eye symptoms: allergic conjunctivitis

■■ clear, watery ophthalmic discharge

■■ redness caused by dilation of the conjunctival blood vessels

■■ ophthalmic itching, sometimes so severe that the sufferer resorts to scratching the eyelids to relieve it

■■ photophobia

■■ skin folds or pleats develop parallel to the lower lid margin, extending from under the eye to the top of the cheekbone.

Differential diagnosis

Allergic rhinitis and the common cold have several features in common. They may be confused with each other but can be distinguished by the differences shown in

Table 23.1.

Symptoms and circumstances for referral

■■ wheezing or shortness of breath, which could indicate asthma

■■ earache or facial pain, as these may indicate sinusitis or otitis media requiring antibiotics

■■ purulent, rather than clear, discharge from the eyes, indicating the possibility of infection

■■ blood in nasal discharge

■■ no improvement after 1 week of treatment with over-the-counter medication.