People use antihistamines to treat their allergy symptoms such as a runny nose, a scratchy throat and watery eyes, as well as to clear congestion of the sinuses. These symptoms are brought on by an allergen response, meaning some foreign material triggers the release of a substance in the body called histamine. Allergy and common cold sufferers may choose from many antihistamines sold over-the-counter without a prescription, but people should not take them unless prescribed by the doctor if they have a diagnosis of glaucoma, prostate problems, diseases of the thyroid, hypertension or diseases of the heart, FamilyDoctor.org recommends.
Brompheniramine
This over-the-counter antihistamine functions to stop the symptoms associated with allergies and or a cold such as sneezing, watery, itchy and irritated eyes and hay fever. It works by therapeutically inhibiting the action of histamine, which causes allergy symptoms. This medication cannot stop the cause of the allergy or increase the speed of recovery. The National Institutes of Health indicate children should not take brompheniramine to induce sleep.
Chlorpheniramine
Chlorpheniramine, another OTC medication also helps treat allergy symptoms, the National Institutes of Health report. By stopping the action of histamine, chlorpheniramine can help reduce congestion in the sinuses.
Dimenhydrinate
Along with helping to decongest the sinuses, this antihistamine also can help reduce nausea, motion sickness and dizziness, the National Institutes of Health reports. This modification also treats Menieres, a disease that affects the inner ear, causing ringing and balance difficulties.
Diphenhydramine
The antihistamine diphenhydramine can decrease congestion while it helps stop rhinitis or a runny nose and other symptoms of colds, flu and allergies. People also may buy it OTC to help fight their insomnia and motion sickness. Physicians may recommend it during the early stages of Parkinson's disease to help control symptoms of shakiness as well as muscle and balance control.
Loratadine
If a person suffers from liver or kidney disease, the antihistamine loratadine can cause problems, Drugs.com indicates. Other people, however, may find relief from congestion associated with hay fever symptoms and allergies. It works by its therapeutic effect in stopping the production of histamine, which occurs during an allergen response.
