Antihistamines and Sinus Relief

Like chronic rhinitis (hay fever), chronic inflammation of the sinuses might be of allergic origin. Exposure to specific allergens leads to the development of allergic sinus symptoms, like itching inside the nose, sneezing, runny nose, headache etc. Whenever allergens come into contact with the body, memory cells in the circulation and in tissue identify the allergen and release substances that mediate the allergic response, the most important substance being Histamine. That is why anti-histamines have a prominent role in the treatment of seasonal allergies like allergic sinusitis and hay fever etc.

How do antihistamines work?

Antihistamines are chemicals that have been found to block the histamine receptor and prevent the binding of histamine with it’s receptors, resulting in an inhibition of histamine effect on tissue, like itching and swelling and redness and sneezing and coughing etc. This same characteristic of antihistamines is what causes the side effects, because it does not only block histamine receptors at the site of the allergy, but instead it blocks histamine receptors in the whole body, often resulting in a number of undesired side effects.

What are some side effects and precautions associated with antihistamines?

1. The most well known side effect is sedation (sleepiness), and it is the rationale behind the use of some antihistamines as sedatives. This might cause problems in children who have to go to school and in adults who must drive or operate heavy machinery, so caution is advised when using antihistamines with sedating effect.
   Some newer antihistamines do not have the sedative effect and can be used safely in adults at risk and whenever sleepiness is not desired, i.e. Loratadine.
   
2. The second most common side effect is dryness of the mouth causing thirst.
   
3. Antihistamines might cause increase in heart rate, if the dose is excessive it might cause palpitations. Some antihistamines have been found to have lethal side effects on the heart when combined with specific antibiotics, like combining Erythromycin and Chlorpheniramine, resulting in prolongation of the QT interval and arrhythmia. That is why doctor’s prescription should be followed carefully and all medicines that were previously prescribed or that the patient is using at their own discretion should be reported to the treating doctor so he can determine whether dangerous interactions exist with antihistamines.
   
4. Antihistamines might worsen pre-existing problems in urination especially when there is an enlarged prostate.
   The dose of antihistamine might need to be reduced or a local or topical type of antihistamine might be used.

Different forms of antihistamines:

Antihistamines can be given as syrup (children) or tablets, as injections (acute symptoms), or as topical preparations (least side effects) like nasal drops and creams. Some antihistamines are used in the form of nasal spray.