Hay Fever: A Guide
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Hay Fever: A Guide
How does pollen make my eyes and throat itch, and my nose run all summer? With so many medications out there, what is the best cure, and how can I avoid my symptoms in the first place?
There are a range of methods which one can use to combat the symptoms of hay fever, and if OTC antihistamine drugs, and corticosteroids do not work, it is certainly worth seeking professional advice, which could potentially lead to immunotherapy. Hayfever, or allergic rhinitis, is an allergic reaction to environmental allergens, such as pollen, dust mites, and animal dander. The first line of treatment includes topical steroids and antihistamines. Oral antihistamines are useful for mild-moderate symptoms such as palatal itch, sneezing and eye symptoms.
Mechanism of action of hayfever
Hayfever, or allergic rhinitis, is an allergic reaction to environmental allergens, such as pollen, dust mites, and animal dander. People who suffer during the spring are often experiencing an allergy to tree pollen, whereas grass pollen is usually the culprit during late spring and early summer. There are two types; an immediate reaction, known as type 1 hypersensitivity, and ongoing rhinitis. Type 1 hypersensitivity occurs when grass pollen interacts with IgE (a type of antibody) on the surface of sensitised mucosal mast cells, which in turn release histamine and leukotrienes as mediators, resulting in symptoms such as itch, nasal congestion and sneezing. Ongoing rhinitis is produced through mucosal dendritic cells or macrophages recognising and processing allergens, stimulating the release of interleukins by T lymphocytes, which cause the production of eosinophils (a type of white blood cell) and IgE. The symptoms include blockage, an impaired sense of smell and nasal hyper reactivity (‘an exaggerated nasal response to environmental irritants such as cold air, perfume, or tobacco smoke’ - S.Durham).
Preventative measures
An obvious precaution which should be taken by hay fever sufferers is to avoid grassy spaces, in particular during the evening and night, when pollen counts at ground level are highest. The humidity indoors should be kept between 30 and 50%, to prevent the growth of mould, and ‘mite-proof’ covers for pillows, duvets, comforters and mattresses can reduce the number of dust mites. Pollen filters can also be installed in cars, and clothes should not be left to dry outside, thus minimising exposure to potential allergens.
A study was carried out in 1996, by Strachan et al., to determine the impact of a higher number of siblings on allergenic sensitisation. The conclusion was that there was a lower prevalence of hay fever throughout children from larger families. Although this may seem to be a study where loose ties are drawn between completely unrelated factors, there is a perfectly logical mechanism that was proposed: younger siblings have increased contact with the allergens during early childhood, with their older siblings bringing pollen into the house, thus leading to protection for the younger siblings against these allergens. This follows on to the practice of immunotherapy, which is a preventative route taken by many patients whose hay fever cannot be controlled by anti-allergy drugs. Immunotherapy is administered in a specialised clinic or hospital, and can either be in the form of allergy shots or sublingual tablets, both of which attempt to build tolerance in the body to the effects of the allergen.
Pharmacological treatments
The first line of treatment includes topical steroids and antihistamines. Oral antihistamines are useful for mild-moderate symptoms such as palatal itch, sneezing and eye symptoms. They work by competing with histamine to bind to receptors on cells, preventing histamine from binding, and thus preventing the symptoms of allergic rhinitis. Short-acting antihistamines can be taken every 4-6 hours, and are helpful to take 30 minutes before exposure to the allergen. Timed-release antihistamines can be taken every 12-24 hours, and are particularly useful for long-term use daily. It is more effective to take antihistamines before the development of symptoms. Taking antihistamines daily builds up its levels in the blood, which also increases the efficacy of the medication.
However, antihistamines do not affect nasal blockage, which is a symptom better treated with topical corticosteroids. These have very few side effects and a high potency and come in the form of sprays and aqueous corticosteroids are better tolerated and distributed in the nose than corticosteroids in fluorocarbon propellants. Side effects include local irritation and sometimes (rarely - 5% cases) bleeding.
The second line of treatment, necessary if a patient does not respond to the above options includes oral corticosteroids, which are particularly useful if nasal blockage has occurred. Another option is taking topical decongestants to allow topical corticosteroid penetration to occur.
Antihistamine overdose
The Canadian Society of Allergy and Clinical Immunology has stated that ‘intolerable and potentially life threatening adverse effects’ can arise from first generation antihistamines. The limit of how much antihistamine one can take safely depends on any other medication taken by the person, the type and amount of antihistamine taken, the age and size of the person, and any preexisting health conditions the person may have. Mixing certain antidepressants and motion sickness drugs with antihistamines can also lead to an overdose. First generation antihistamines include brompheniramine, chlorpheniramine and diphenhydramine (Benadryl), whereas second generation antihistamines are those which do not cause jitteriness or drowsiness, like first generation antihistamines. They include cetirizine, fexofenadine and loratadine. Overdose of second generation antihistamines is, generally less serious than first generation. This is because first generation antihistamines have an increased ability to cross the blood-brain barrier (hence, the dizzy / drowsy effects). Symptoms of antihistamine overdose include flushing, dilated pupils, a fever, tachycardia (increased heart rate), hypotension (decreased blood pressure), urinary retention and coma. In the case of an overdose, the nearest poison centre should be called. Severe symptoms would warrant a 999 call.
Conclusion
There are a range of methods which one can use to combat the symptoms of hay fever, and if OTC antihistamine drugs, and corticosteroids do not work, it is certainly worth seeking professional advice, which could potentially lead to immunotherapy. There has also been interesting results from studies looking into alternative treatments, such as spirulina, which has been correlated with reducing nasal congestion, by inhibiting the formation and activity of mast cells (which contain histamine, causing the swelling and inflammation of cells).
In terms of more traditional medication, take a look at the flow chart I have created, which can serve as a base for understanding the myriad of options available when you approach the hay fever section of the pharmacy. Don’t lose hope - you can still have a picnic on the grass without itchy noses, running eyes and sore throats!
The following resource is a flowchart which enables people to determine which treatment would work best for them. The drugs which are in italics are classified as drowsy. This is purely meant to serve as a guide - a doctor must always be consulted in the case of prescription medicine.
Bibliography:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1112773/
https://acaai.org/allergies/allergic-conditions/hay-fever/
https://www.medicalnewstoday.com/articles/antihistamine-overdose#summary
https://adc.bmj.com/content/74/5/422.info