Antihistamines are a common medication used to treat allergy symptoms that affect the nose, eyes and throat, according to NHS.uk. Most antihistamines are available over-the-counter in pill form for use without a prescription. Antihistamines are classified into two groups: sedating and non-sedating. Any medication used to treat or prevent a condition needs to be evaluated by a doctor; therefore, do not use antihistamines without first talking with a medical professional.
Function
According to Net Doctor, the human body releases antibodies to fight off allergens. The body produces these antibodies that begin a chain reaction that leads to increased histamine levels, which produces common allergy symptoms such as sneezing, irritated eyes and an itchy throat. The purpose of antihistamines is to block the effects of histamines in the body. All types of antihistamines function to prevent the immune system from releasing histamine.
Sedating Antihistamines
Net Doctor states that sedating, or first-generation, antihistamines are noted for causing extreme drowsiness. The most common active ingredient drugs that cause sedation are brompheniramine, chlorpheniramine, dimenhydrinate, diphenhydramine and doxylamine. These antihistamines work by suppressing the central nervous system, which causes tiredness. Sedating antihistamines are also used to treat motion sickness, dizziness and insomnia, according to NHS.uk. Sedating antihistamines are also preferred for a sudden allergic reaction because of their fast-acting ability.
Non-Sedating Antihistamines
Non-sedating, or second-generation, antihistamines are more common because of their ability to prevent histamine without drowsiness, according to the American Academy of Otolaryngology. Non-sedating antihistamines, such as loratadine and cetirizine, are typically sold in single daily doses. These antihistamines often take longer to affect the histamine levels in the body and are used on a daily basis for prevention and treatment of seasonal allergies.
Side Effects
Antihistamines can cause side effects that need to be considered before use. Before taking an antihistamine the patient should talk to the doctor if she has hyperthyroidism, hypertension, an enlarged prostate, glaucoma or a stomach ulcer, according to Drugs.com. Other common side effects of taking an antihistamine may include dry mouth, dizziness, headaches, drowsiness and nausea, according to Net Doctor. Pregnant or breastfeeding women should talk with their gynecologist before taking antihistamines.
Precautions
Antihistamines can cause marked drowsiness, which can prohibit someone's ability to function normally. While taking an antihistamine, especially a sedating antihistamine, avoid driving, making life-altering decisions or operating heavy machinery. Check OTC product labels to identify the different drugs used in the product such as decongestants, expectorants, pain relievers and other antihistamines. Many OTC allergy and cold drugs contain more than one drug that could lead to an overdose if not taken with caution.
