1 in 5 men and women, boys and girls have hayfever.80% of people will have it by age 20 or earlier.Hayfever in medicine lingo is called allergic rhinitis, which means what this condition is, is an allergic reaction limited to the nose and sinuses, which can however affect other areas of the body like the eyes, pharynx, eustachian tubes or ears, or make other preexisting conditions worse, like for example asthma.
Here’s what happens: Your immune system gets sensitized to a foreign protein, be that a protein from pollen, or dust, or mold, or whatever else, from pets to flour or bird poo.Now this tendency to get sensitized to certain proteins has a genetic component.So in those susceptible individuals, the body produces antibodies (immunoglobulins) of the IgE variety that are directed against the foreign protein.And once the protein arrives in your nose, IgE binds to it.IgE sits on the surface of so-called mast cells in the mucosa of the nose, and once the IgE+foreign protein complex activates the mast cell, all immunological hell breaks lose, and mediators like Histamine, Leukotrienes and Tryptase get released that start the immune reaction which leads to your nose swelling up and your eyes itching, and all those other symptoms that make spring such a great time of year for sufferers.
These mediators, via various interactions, ultimately lead to the symptoms of hayfever (ie, nasal congestion, sneezing, itching, redness, tearing, swelling, ear pressure). Mucous glands are stimulated, leading to increased secretions. Vascular permeability is increased, leading to plasma exudation. Vasodilation occurs, leading to congestion and pressure. Sensory nerves are stimulated, leading to sneezing and itching. All of these events can occur in minutes; hence, this reaction is called the early, or immediate, phase of the reaction.Then over the next 4-8 hours a later phase sets in, with recruitment of other inflammatory cells, that maintain and entertain the allergic reaction.There may be associated symptoms like feeling sick(malaise), fatigue and drowsiness.
While hayfever is annoying and can severely reduce quality of life, the mortality is low and morbidity comes mainly from things like the worsening of a preexisting asthma condition, or from otitis media or sinusitis or dermatitis.
Most cases are seasonal, but there are also forms where patients will show symptoms all year round.
Rhinitis can be caused by all sorts of things, from medications or hormones to pregnancy to vasomotor susceptibility, and these causes should be considered, but usually the diagnosis of hayfever is not a problem, if the typical symptoms like nasal congestion, itching and swelling are present, together with an onset of symptoms before 20 years of age and a positive family history.
As to testing, obviously allergy tests to see which allergen is causing the immune reaction leading to the hayfever can be useful, but often avoidance of the culprit protein isn’t possible, or the person will have reactions to multiple agents.Blood tests for levels of IgE or eosinophils are unreliable, because their sensitivity is not great.50% of hayfever patients have normal IgE blood levels.
Now, as for the treatment of hayfever, there are 3 aspects to this.
One is allergen avoidance.This can work when the culprit is identified, and one is able to avoid it, like say, cat hair, or certain mold, but it might not be practicable in the case of, say, pollen, although pollen concentration is highest on dry, warm and windy days.
Two is drugs.Mainstay here is the antihistamines and mast cell stabilisers, and decongestants like Pseudoephedrine.For patients with perennial or chronic symptoms an intranasal steroid spray can be useful.The antihistamines of the second generation are all “non-drowsy”, and Promethazine(Phenergan) is the only first-gen antihistamine left in use, as a tablet or intravenously in the emergency setting, although its use has been associated with increased mortality in anaphylaxis.Those drugs compete with Histamine for the so-called H1 receptor on mast cells, and are great in reducing the symptoms of sneezing and itching.They don’t however have a good effect on the nasal congestion, so that’s where the decongestants come in.There are combination preparations available that contain both, that are first-line treatment of choice for acute seasonal hayfever.
Three is immunotherapy, which essentially means desensitization.This is like vaccination for allergy, and it’s a process that takes 6-12 months for results to show, but it works for 80-90% of people, and needs to be continued for 3-5 years.This therapy seems to work particularly well for allergy to pollen, dust mites and cats.