Is it hay fever?

Dr Mike Townend examines the causes of allergic rhinitis and discusses how to confirm a diagnosis of hay fever and subsequently treat the condition

Allergic rhinitis is a syndrome consisting of inflammation and swelling of the nasal mucosa, with variable degrees of nasal obstruction, hypersecretion of mucus and sneezing, occurring on exposure to airborne allergens. It is often associated with allergic conjunctivitis, and about 40 per cent of sufferers also have or develop asthma^1,2,3. When the syndrome occurs in response to allergens derived from grass or grass pollen it is referred to as hay fever.

Hay fever is confined to the summer months when grass pollens become airborne, usually occurring during the months of June, July and August, though its precise time of onset depends on weather patterns, pollen counts in the atmosphere being higher in warm, dry conditions. Its peak occurrence often coincides with important academic examinations in the UK school calendar, with potentially detrimental effects on academic performance.

Diagnosis

Hay fever is diagnosed principally from its symptoms of nasal obstruction (running and sneezing) and/or red, itchy eyes, and from its onset and duration in the summer months. Examination of the nose confirms swelling of the mucosa, which often has a pale violet rather than a red colour. If the eyes are affected the orbital conjuctiva is injected, often worse in the angles but often widespread, and there may be a 'cobblestone' pattern on the palpebral conjunctiva. Allergic conjunctivitis may also be distinguished from the infective variety by the predominance of itching rather than grittiness or soreness.

A history of rhinitis and/or conjunctivitis beginning in late spring or early summer and lasting until mid to late summer is so characteristic that skin testing is probably unnecessary in most cases. Some patients may have co-existing symptoms due to other airborne allergens which may not be seasonal and may confuse the diagnosis. There may also be co-existing asthma which may or may not be seasonal.

Allergic rhinitis

Allergic rhinitis may be caused by other common airborne allergens including those derived from house dust mites and animals such as cats, dogs or horses. In such cases, symptoms are present at other times in addition to the summer months and a history of exposure, for example to domestic animals, may be obtained.

Other possible causes of allergic rhinitis which are not confined to the summer may be found in occupational exposure to allergens (see Table 1) and a careful occupational history should be taken. For workers exposed to these allergens, allergic rhinitis is a 'prescribed industrial disease' and in some cases industrial disability benefit may be payable.

It is possible that some patients may have a reaction to more than one type of airborne allergen, and hay fever may then co-exist with dust, animal or occupationally derived allergic rhinitis.

Vasomotor rhinitis is similar to allergic rhinitis in its symptoms but persistent running of thin, clear mucus is often a predominant symptom. No clear history of reaction to allergens is obtained but there may be a history of symptoms on exposure to changes in environment such as atmospheric temperature or on being exposed to direct sunlight.

Treatment

Antihistamine drugs have been shown to be a safe and effective treatment for hay fever4, for both nasal and ocular symptoms. Their effect, as may be expected, tends to be greater on the immediate, histamine-related symptoms such as itching and sneezing than on nasal obstruction. Older, sedative antihistamine drugs were often associated with drowsiness, impairment of decision making and verbal learning and reduced psychomotor skills⁵, though hay fever itself may also cause some of these problems if untreated⁶. Newer, non-sedative antihistamines, for example, acrivastine (Semprex), cetirizine (Zirtek), fexofenadine (Telfast), loratadine (Clarityn), mizolastine (Mizollen), have been shown to be a safer alternative and to reduce the sedation caused by the hay fever itself, a boon to those sitting or reading for important examinations in the summer. Semprex and Clarityn can also be used for children over two years old.

Intranasal corticosteroids

⁷ are often extremely effective in reducing the symptoms of hay fever and are much more effective than antihistamines in reducing nasal obstruction. They have an effect on the immune system at virtually all levels of the 'inflammatory cascade'⁷ and have been shown to be superior to antihistamines in reducing all nasal symptoms and in increasing the number of symptom-free days. There is no statistically significant evidence of adrenal suppression from the use of intranasal corticosteroids⁸. Although one study of growth in children has suggested that there may be a reduction in short-term lower leg growth⁹, there is no evidence that this can be extrapolated to a significant reduction in final adult height. If symptoms are severe, initial use of betamethasone nasal drops may be justified, but for longer-term treatment, it is advisable to use a less well systemically absorbed corticosteroid such as beclomethasone (for example Beconase) or mometasone (Nasonex).

Other nasal preparations for hay fever include sodium cromoglycate (Rynacrom) and nedocromil (Tilarin)¹⁰_ mast cell stabilisers which reduce the release of histamine from mast cells. They may be effective in reducing nasal symptoms, particularly itching and sneezing. Levocabastine (Livostin) is a potent antihistamine also available as an intranasal preparation and may be more effective than sodium cromoglycate.

Oral corticosteroids are not justified for routine use in hay fever, though a short high dose course of prednisolone for up to 1 or 2 weeks (1-2 mg/kg/day for children under the age of 1 year, 20 mg/day from 1-5 years and 30-40 mg/day for adults and older children) may be used for the initial control of severe or disabling symptoms. Such a course of treatment is commonly used in acute severe asthma. Maintenance treatment with 2.5-10 mg/day may be used as a follow-on treatment until control is achieved by other means or for a further limited period, for examle to cover the summer examination season in a child whose severe symptoms may prejudice academic achievement.

Depot injectionsof corticosteroids such as triamcinolone (Kenalog) and methylprednisolone (Depo-Medrone) may be used to treat both the nasal and eye symptoms of hay fever^11,12. Their effect lasts for four weeks or more, and the injection may need to be repeated at least once in order to maintain control throughout the hay fever season. The injection is more effective given at the start of the season or early in it while the pollen count is still increasing¹².

The use of depot injections has been shown to be more effective than intranasal steroids and to cause less adrenal suppression than oral prednisolone 7.5 mg/day. There is little information available on the possibility of suppression of growth in children following the use of depot steroid injections for hay fever but it seems unlikely that if treatment is confined to the short hay fever season that there will be any significant retardation of growth. Depot steroids should be given by deep intramuscular injection because surface leakage may lead to skin atrophy. The use of depot steroid injections should be limited to patients with severe symptoms which are difficult to control by other means, particularly if they are at the stage of important academic examinations or other life crises. In such patients an injection immediately prior to the start of the hay fever season and repeated if necessary after four weeks may have a transforming effect on the patient's life.

Treating the eyes. It is easy to overlook the intense irritation which some hay fever sufferers experience in their eyes. Both sodium cromoglycate (Opticrom)¹³ and nedocromil sodium (Rapitil) are available as eye drops and are frequently effective. Levocabastine¹⁴ is an antihistamine which is available as eye drops and combines effectiveness with a rapid onset of action

Mike Townend is a general practitioner in Cumbria and a member of the British Travel Health Association

References
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