What are antihistamines and how do they work?
Antihistamines are a class of drugs that are used to treat various allergic conditions. They work by blocking the effects of histamine, a chemical that is released by your immune system when it encounters an allergen, such as pollen, dust, or pet dander. Histamine causes symptoms such as sneezing, itching, runny nose, watery eyes, and inflammation. By preventing histamine from binding to its receptors on cells, antihistamines can reduce or eliminate these symptoms.
Types of antihistamines
There are two main types of antihistamines: first-generation and second-generation. First-generation antihistamines are older drugs that have been available for decades. They tend to cause more side effects, such as drowsiness, dry mouth, dizziness, and blurred vision. They can also interact with other medications and impair your ability to drive or operate machinery. Some examples of first-generation antihistamines are diphenhydramine (Benadryl), chlorpheniramine (Chlor-Trimeton), and hydroxyzine (Atarax).
Second-generation antihistamines are newer drugs that have been developed in the last few decades. They are less likely to cause drowsiness and other side effects, although they may still do so in some people. They are also less likely to interact with other drugs or affect your mental or physical performance. Some examples of second-generation antihistamines are cetirizine (Zyrtec), loratadine (Claritin), and fexofenadine (Allegra).
Uses of antihistamines
Antihistamines are mainly used to treat allergic conditions, such as hay fever, hives, food allergies, insect bites or stings, and drug reactions. They can help relieve symptoms such as itching, swelling, redness, and rash. They can also reduce nasal congestion and sneezing by drying up the mucus in your nose.
Some antihistamines can also be used for other purposes, such as:
- Inducing sleep: Some first-generation antihistamines have a sedating effect that can help you fall asleep faster and stay asleep longer. They are often found in over-the-counter sleep aids or combined with pain relievers.
- Preventing or treating motion sickness: Some first-generation antihistamines can prevent or reduce nausea and vomiting caused by motion sickness. They are often taken before traveling by car, plane, boat, or amusement park ride.
- Reducing anxiety: Some first-generation antihistamines have a calming effect that can help you cope with stress or anxiety. They are sometimes used as a short-term treatment for mild anxiety disorders.
- Treating some symptoms of Parkinson’s disease: Some first-generation antihistamines can help reduce tremors, stiffness, and drooling caused by Parkinson’s disease. They are usually used as an adjunct therapy to other medications for this condition.
Side effects of antihistamines
Antihistamines are generally safe and effective when used as directed. However, they may cause some side effects in some people. The most common side effects of antihistamines are:
- Drowsiness: This is more common with first-generation antihistamines than with second-generation ones. It can affect your alertness and concentration and increase your risk of accidents or injuries.
- Dry mouth: This can make your mouth feel sticky or uncomfortable and increase your risk of dental problems.
- Dizziness: This can make you feel lightheaded or unsteady and affect your balance and coordination.
- Blurred vision: This can make it hard to see clearly or focus on objects.
- Constipation: This can make it hard to have regular bowel movements and cause abdominal pain or discomfort.
- Urinary retention: This can make it hard to empty your bladder completely and cause urinary tract infections or kidney problems.
Some people may also have an allergic reaction to antihistamines themselves. This can cause symptoms such as hives, swelling, difficulty breathing,