Allergic Rhinitis
13
March

By Adem Lewis / in , , , , , , , , , , , , , , , , /


This is Doctor Ankoor Shah, and this is a talk on allergic rhinitis entitled allergic rhinitis, nothing to sneeze at. In this talk, we will give a brief overview of allergic rhinitis. In particular, we will cover some of the clinical features of allergic rhinitis, and touch on some of what’s known about the pathophysiology of this disorder. Finally, we will talk about the therapeutics that are out there, and how we use them to help our patients. Here’s the basic outline of this talk. We’ll start with the patient presentation and then go through the various topics listed here. First, let’s start with the patient case. This is one that I’m sure that many of you will be personally familiar with. An 18-year-old female, who for many years has had symptoms a runny nose as well as seasonal congestion in the springtime, now complains of year-round symptoms with a rhinorrhea and congestion leading to headaches as well as red, itchy eyes. When you examine her, her conjunctiva are injected and red. On otoscopic exam of the nasal passages, you see pale, boggy turbinates bilaterally with some thin, clear mucus present. Based on her physical and history, you make a preliminary diagnosis of allergic rhinitis. So how do we actually define allergic rhinitis? Allergic rhinitis refers to the inflammation of the nasal membranes in response in environmental allergens with manifestations including sneezing, rhinorrhea, conjunctival irritation, and sinus inflammation and congestion. Symptoms can occur seasonally or year round depending on the particular allergens to which the patient is sensitive to. Allergic rhinitis is common. While the prevalence varies, in the US, approximately 20% of adults have allergic rhinitis, while as many as 40% of children do. In children, it does tend to be more common in boys, although gender differences even out in adulthood. An increased prevalence has been observed in urban areas, and overall it appears that prevalence is on the rise. There are a number of theories for this, one of which is the hygiene hypothesis, which, very briefly, postulates a better hygiene resulting in decreased microbial exposure, leads to an increase in allergic disease. As one can guess through the prevalence of disease, symptoms of allergic rhinitis can lead to decreased productivity and loss of work days, making it a huge economic burden. The main clinical features a patient will discuss with you are sneezing, rhinorrhea, nasal itching, and nasal obstruction. On exam, you may see in both children and adults an allergic salute, or a nasal crease, seen in this picture. Eyes may be injected or red, and may have darkening and swollen edema under the eyelids, creating what are called Dennie-Morgan lines. Nasal exam frequently demonstrates enlarged, pale, blue, and swollen mucosa of the turbinates, which can block the nasal passages. Most patients have symptoms year round, particularly if there are dust mite or pet allergies. Some pollens do have a seasonal predilection, however. Tree pollen counts usually begin to rise in late winter into spring, grass pollen counts from spring until early autumn, and weeds from late summer through autumn. So what is the pathophysiology of this disease? The immunology is complicated, but basically, one of the first steps is sensitization, where a person with a tendency towards allergies produces an antibody which is of an IGE subtype, specific to a particular antigen or allergen. An allergen is a protein, like a pollen for example, which produces an allergic reaction. At the cellular level, a specific cell within the immune system called a T-helper, specifically a Th2-helper, cell facilitates this process by producing pro-allergy cytokines, including interleukin four, five, and 13. IGE binds to receptors on the main allergy cells, called mass cells and basophils, that lead to production of histamine, prostaglandins, and leukotrienes, all of which propagate allergic inflammation. There are two phases, an immediate one that occurs in 30 minutes, and a later one that has a greater contribution from the basophils, which can occur several hours later. Allergic rhinitis is primarily diagnosed by history and physical. This is supported by the use of immediate hypersensitivity skin prick tests. The main allergenic protein is placed in the epicutaneous part of the skin. After 15 minutes, if the patient is sensitized to the allergen, a wheal , or raised circle with induration, and/or a flare, or redness, will appear. Serum tests are used if patients cannot come off antihistamines due to symptoms, or it skin tests do not correlate with clinical history. The first step in treatment, although not always possible, is avoidance of the offending allergen. Patients with dust mite allergy should cover their bedding with dust mite covers. Bed sheets should be changed frequently and washed in hot water. Pets should be kept out of the bedroom and moldy areas should be cleaned. In terms of medications, the most effective maintenance therapy is intranasal glucocorticoids. Antihistamines are used as rescue medications to quickly relieve or prevent nasal and eye sometimes. Finally, montelukast, which is an antagonist to the leukotriene receptor, is also used. If medication avoidants are not fully effective, immunotherapy is utilized. Vaccines comprised of allergens a patient is sensitized to are injected in a build up fashion, subcutaneously starting on a very dilute concentration and slowly increased to an effective or maintenance concentration. Immunotherapies continue for three to five years, and can be highly effective in treatment of allergic reactions. Some practices, particularly in Europe, are beginning to employ sublingual immunotherapy drops, but this practice has not been accepted widely in the United States. While allergic rhinitis is clearly not a deadly disease, it can be associated with significant morbidity and can definitely affect one’s quality of life. Notably though, even without treatment, symptoms do tend to improve with age. In summary, allergic rhinitis is a common disorder marked by perennial nasal and eye symptoms do the immune sensitization and production of specific IGE antibodies. Diagnosis is made clinically and with skin prick testing. Treatment mainly consists of allergen avoidance, intranasal steroids, and antihistamines. However, allergy immunotherapy remains a highly effective therapy for severe or persistent cases, though at the expense of cost and patient time. Here are some key references for you to learn more about allergic rhinitis.


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