Allergic Rhinitis is defined as inflammation of the lining of the nasal cavity as a result of an allergic response. The more common allergens are inhalant such as house dust mite(figure 1), pollens, grasses, cockroach and animal dander like dogs and cats. The other group of allergens that can cause a reaction in the nose and throat is food allergy. Patients can be allergic to a particular food type which can result in swelling of the nose and production of mucous. While the pathogenesis of inhalant allergies is well understood and is known to be related to histamine release, the mechanism for food allergy is less well understood and is a topic of controversy. Although certain foods are related to histamine such as shellfish, peanuts and can cause severe allergic reactions that are potentially fatal (anaphylaxis), the majority do not cause histamine-related symptoms.
Symptoms and Signs
|Nasal symptoms from allergy include
Our centre offers testing for nasal allergies. Skin prick test (figure 3) is readily available for the following allergens; house dust mite, cockroach, ragweed, dog and cat dander. This test is performed in the clinic and is suitable for cooperative children. Results are available in about 15 minutes. A blood test (RAST) measuring specific immunoglobulins to allergens is also available. The test requires a blood sample and results are available in 2 weeks.
Food allergy testing in the form of intradermal provocation food test (IPFT) is also available in collaboration with allergy colleagues. Some immunologists and allergists consider this form of testing controversial. It involves injecting extracts of suspected foods into the dermis of the skin and observing for a reaction after 10 minutes (figure 4). Since the dermis is involved, each injection is painful. Adults are generally able to tolerate the pain but children under 13 years are subjected to a general anaesthesia if this test is done.
The principles in the management of allergic rhinitis are;
1. Allergen Avoidance – In the case of house dust mite allergy, avoidance therapy should start in the home environment (http://www.allercare.com.sg/house_dustmite/index.htm). The following measures can be taken;
• Change bed linens every week, pillow cases daily,
• Wash bedding in hot water to kill mite
• Remove carpeting, drapes, wall hangings and other dust accumulators
• Wet mop and vacuum frequently
• Replace stuff toys with metal, wooden and plastic ones
• Dehumidifiers and air purifiers to reduce humidity and mite concentration in the air
Unfortunately, it is nearly impossible to achieve a dust-mite free room and adjunctive treatments are required.
2. Pharmacotherapy(Figure 5) – this includes the use of nasal steroid sprays (eg. Flixonase, Nasonex), topical decongestants (eg. Otrivin, Iliadin nose drops/ spray), oral antihistamines (eg. Clarityne, Telfast, Aerius) and mast cell stabilizers (eg. Cromolyn). These agents are very effective and relative inexpensive. Nasal steroid sprays and oral antihistamines can be used for many years without side effects. Topical decongestant sprays like Afrin should be used sparingly. The downside of pharmacotherapy is the fact that they serve only as a control and require continual use to maintain control of allergic symptoms.
3. Immunotherapy – Please see below
4. Surgery for Nasal Obstruction – A simple clinic procedure called radiofrequency turbinate reduction (RTR) can be performed under local anesthesia to relieve nasal obstruction resulting from swollen turbinates for the long term. This painless procedure aims to shrink swollen turbinates using electrical energy. (please see under Commonly Performed Clinic Procedures)
Medical therapy with nasal steroid sprays and oral antihistamines is effective in controlling symptoms of nasal allergy such as itching, sneezing, nasal blockage and rhinorrhea. However, the recurrence of symptoms once medical therapy ceases continues to be a source of frustration and unhappiness with some patients. Immunotherapy is the closest to finding a definitive long term solution for allergic rhinitis.
The principle of immunotherapy is to desensitize the patient to a particular allergen by altering the immune system’s response to an offending allergen. In an allergic patient, exposure to an offending allergen results in an overly aggressive response from the immune system. This results in swelling, production of mucous and itching. Immunotherapy aims to modify this overly aggressive response so that exposure to the offending allergen does not result in the undesired response. The current form of administration is Sublingual Immunotherapy (SLIT), Staloral. It is clinically proven with more than 10 published trials to date (and more on the way).
How is it administered?
Once the allergen is identified using skin prick test or a blood test, the corresponding SLIT can be ordered. The treatment consists of an initiation phase and a maintenance phase. The initiation phase last about 11 days and the recommended duration for the maintenance phase is for about 3 to 5 years. Patients apply the drops daily under their tongue (sublingually), hold it for 2 minutes and swallow (figure 5). It’s that simple. The treatment is home-based which makes it convenient and time-efficient.
(please see the following links for details of the regimen
Pros and Cons of Immunotherapy
Are there any risks?
With more than 50 million doses recorded, no serious adverse reaction has been reported. Hence, unlike traditional immunotherapy (which is injected and associated with a small risk of anaphylaxis) SLIT is very safe. It is also very suitable for children 3 years and older.
MBBS (S'pore), FRCS (Edin), FRCS (Glasg) Fellow, Otology / Neurotology (Can)
This page is dedicated to Prof Yeoh Kian Hian