Nasal allergy and hay fever

What is an allergy?

An allergy is an immune-system reaction to a substance that is usually harmless. These substances, called allergens, include pollen, animal dander, house-dust mites and moulds. In a person with an allergy, the immune system reacts to an allergen by releasing histamine and other inflammatory substances. Nasal allergy can cause:

• A blocked nose
• Sneezing
• A runny nose
• Watery eyes
• Itching of the eyes, nose or throat

Irritants such as tobacco smoke, perfume or paint fumes can cause similar symptoms without an allergic immune reaction. They can irritate anyone and can also worsen an existing allergy.

What is hay fever?

Hay fever, or seasonal allergic rhinitis, is an allergy to airborne pollen from trees, grasses and weeds. Despite the name, it is not caused by hay and does not usually cause fever. Symptoms include:

• Sneezing
• A runny or blocked nose
• Itching of the eyes, nose or throat
• Watery or red eyes
• In people with asthma: chest tightness, shortness of breath or wheezing

Allergic rhinitis may be seasonal or present throughout the year, depending on the allergen. House-dust mites, animals and moulds can cause perennial symptoms.

What happens inside the nose?

The inside of the nose is lined by mucous membrane containing glands and blood vessels. It produces mucus that keeps the surface moist and helps trap particles and organisms. During an allergic reaction, the lining becomes inflamed, the blood vessels swell and mucus production increases. This produces congestion, sneezing and discharge.

Allergy assessment by an ENT specialist

Assessment starts with questions about the pattern, timing and triggers of symptoms and an examination of the nose. A skin-prick test may then be used. Drops containing small amounts of selected allergens are placed on the skin and the surface is gently pricked. The size of any wheal is compared with positive and negative controls. The result must be interpreted together with the history; a positive test alone does not always mean that an allergen causes symptoms.

A blood test for allergen-specific IgE can be useful when skin testing is unsuitable or when confirmation is needed. A nasal provocation test, in which a suspected allergen is applied to the nose under controlled conditions, is only required in selected cases.

Which medicines may be used?

Preventive anti-inflammatory treatment

• Corticosteroid nasal sprays: when used correctly and regularly, these are effective at reducing inflammation and nasal blockage.

Treatment for existing symptoms

• Antihistamines: tablets, nasal sprays or eye drops can provide relatively rapid relief from sneezing, itching and discharge. Cromoglicate sprays or eye drops may be suitable for some milder symptoms.
• Combination nasal sprays: products containing both a corticosteroid and an antihistamine are available for selected patients.

The doctor or pharmacist can explain the correct technique, possible side effects and whether treatment is suitable for you.

Allergen immunotherapy

Immunotherapy can reduce sensitivity to a confirmed allergen and lessen symptoms over time. It is considered when avoidance and medication do not provide sufficient control and when the relevant allergen is clear. Options include:

• Subcutaneous immunotherapy: injections are given in a medical setting, often for pollen and in selected cases for house-dust mite or animal allergy. Treatment commonly continues for three to five years, with a build-up phase followed by maintenance injections.
• Sublingual immunotherapy: a tablet or drops are placed under the tongue. Treatments are available for selected grass-pollen and house-dust-mite allergies. The first dose is usually taken under medical supervision, followed by regular treatment at home for the prescribed period, often about three years.

Immunotherapy can cause allergic reactions and must be prescribed and monitored by a suitably trained clinician. Seek urgent help for severe breathing difficulty, swelling of the tongue or throat, or signs of anaphylaxis.