Q: I have been taking an antihistamine for weeks to deal with my hay fever. I have been feeling very unwell — fatigue, dry mouth — and I was wondering if it could be related to the antihistamine? I am very hesitant to stop taking it as it really does help with my runny eyes and nose.
Dr Grant replies: Hay fever, also known as rhinosinusitis, can begin at any age but generally first starts in childhood/young adulthood. The risk of developing hay fever is higher in those with a family history or people who already suffer with asthma and/or eczema.
Rhinosinusitis is a reaction to small airborne particles called allergens that cause the mucosal lining of the nose and/or sinuses to swell resulting in sneezing, runny nose, and nasal obstruction, often accompanied by itching of the eyes, nose, and palate. It is not necessary to perform allergy testing as the diagnosis is made during taking a history and examination. However, it can be helpful to identify what exactly is causing your symptoms. There are over 30 different types of pollen and 20 types of spores that can trigger hay fever.
By identifying your specific allergens, it may help you avoid them and will highlight if you can seek immunotherapy, which can eventually reduce reliance on long-term medication use.
Antihistamine medication antagonises histamine activity at H1 receptors responsible for inflammation and allergic responses. The first-generation H1 antagonists, are also known as ‘sedating’ antihistamines (e.g. diphenhydramine, chlorpheniramine) as they commonly cause drowsiness. They are often used as sleep aids due to this side effect. If you are taking one of these it could easily be the cause of your recent fatigue and dry mouth. The second-generation H1 receptor blockers, also known as ‘non-sedating’ antihistamines (e.g. loratadine, cetirizine) are less likely to cause drowsiness, fatigue or dry mouth. This is because the non-sedating antihistamines act as selective antagonist of peripheral H1-receptors and are relatively free of anticholinergic activity.
If your symptoms are limited to your eyes, I suggest trying topical antihistamine eye drops, either OTC or prescribed by your GP. The scientific data suggests that topical steroid eye drops (unfortunately not safe to use in the long term) or nasal sprays (can be used for several months every year) are the most effective single maintenance therapy for hay fever.
There are new treatments for hay fever that might allow you to be able to stop all antihistamine use. There are two highly effective treatments, the first is called allergen immunotherapy by sublingual immunotherapy (SLIT). It is given as either a dissolvable tablet or as an aqueous or liquid extract. It is taken daily for three years. The majority of studies of SLIT have been performed with grass pollen allergens in patients with allergic rhinitis but recently house dust mite and birch tree pollen SLIT has become available. SLIT not only treats your hay fever as effectively as steroids and antihistamines, but it also retrains your immune system to be ‘less allergic’.
The second is called rhinolight intranasal phototherapy. In inserts a nasal endoscope into the nostril that emits ultraviolet A, UV-B, and visible light to reduce inflammation and the symptoms while also helping to partially desensitise the nose and sinuses against allergies. It is painless and does not cause any tissue damage. It is effective for the majority of allergic rhinitis triggers.
Dr Jennifer Grant is a GP with Beacon HealthCheck