Antihistamines are medications used to relieve the symptoms of allergic reactions by blocking the effects of histamine, a substance released in the body during allergic reactions. Histamine plays a central role in allergic symptoms such as itching, sneezing, runny nose, eye irritation, and skin rashes. Antihistamines are commonly used to treat hay fever (allergic rhinitis), urticaria (hives), conjunctivitis (eye inflammation), and in some cases, eczema and asthma.
Classes of antihistamines
Antihistamines are divided into two main classes:
- First generation (sedating) : These older antihistamines can cause drowsiness and impair reaction time. Examples include diphenhydramine (Benadryl) and chlorpheniramine. They not only target histamine but can also affect other receptors in the body, leading to side effects such as dry mouth, blurred vision, and urinary retention.
- Second generation (non-sedating) : These newer antihistamines are more specific to histamine receptors and generally do not cause drowsiness. Examples include cetirizine (Zyrtec), loratadine (Claritin), and fexofenadine (Allegra). They are suitable for daily use and impair reaction time less.
Areas of application
- Allergic rhinitis : Both generations of antihistamines can be used to relieve sneezing, runny or blocked nose, and nasal itching.
- Conjunctivitis : Antihistamines relieve itching, redness and swelling of the eyes.
- Urticaria and angioedema : They can reduce itching and swelling of the skin.
- Insect bites and stings : For the relief of itching and swelling.
- Mild allergic skin reactions : To reduce itching and rashes.
Side effects
While second-generation antihistamines are less likely to cause side effects, some people may still experience mild side effects such as headaches, dry mouth, dizziness, and gastrointestinal upset. First-generation antihistamines can cause more severe side effects such as drowsiness and impaired reaction time, which is particularly important to consider when driving or operating machinery.
Important to note
- Antihistamines can interact with other medications, so it is important to consult a doctor or pharmacist before taking them with other medications.
- Pregnant or breastfeeding women should only take antihistamines after consulting a doctor.
- Specific dosages and formulations are available for children, and they should be taken under the guidance of a doctor.
Antihistamines are an effective way to relieve allergy symptoms, but as with all medications, it is important to read the instructions on the package insert and seek medical advice if you have any concerns.
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