Imagine suddenly having red bumps on your body that start itching, or sneezing and a runny nose... When an allergy like this comes to mind, most of us think of an antihistamine pill, right? But did you know that these antihistamines are not all the same, they come in two generations, and their actions and side effects are different? Today, let's talk about this in a simple way.
Why do we need antihistamines?
Simply put, when something we don't like, that is, an allergen, enters our body, some cells in our body's immune system release a chemical called 'histamine.' This is like a warning siren that sounds when an enemy is approaching the country.
This histamine is responsible for many of the discomforts we experience during an allergy.
- Itching and hives
- Runny nose and nasal congestion
- Itchy and red eyes
- Continuous sneezing
- Sometimes nausea and vomiting
So, the class of drugs called antihistamines works by blocking the action of that chemical called histamine. That's like 'muting' the siren. This controls the symptoms of allergies.
Old and new generation antihistamines
Antihistamines can be divided into two main generations: first-generation and second-generation. Let's look at the main differences between the two.
| Attribute | First generation (old varieties) | Second generation (new varieties) |
|---|---|---|
| Drowsiness | Too much. Causes dizziness and drowsiness. | Very little or no sedation (Non-sedating). |
| Effect on the brain | It easily crosses the blood-brain barrier and enters the brain. | It hardly crosses the blood-brain barrier. |
| Active time | It usually lasts for a short time, about 4-6 hours. You have to take it several times a day. | It usually lasts about 24 hours. It is enough to take it once a day. |
| Side effects | Dry mouth, dry eyes, blurred vision, constipation, and difficulty urinating are common. | Side effects are very few. |
First-Generation Antihistamines
These are the first introduced, older type of antihistamines that we all know well. The very popular Chlorpheniramine in our country, that is, the medicine you know as 'Piriton', belongs to this group.
These medications travel through the bloodstream and easily enter the brain. That's why they make you feel very sleepy and dizzy when you take them. Sometimes, doctors may use this sleepiness to prescribe these medications for conditions like itching that keeps you awake at night.
Important: Do not drive, work at heights, or operate machinery while taking this type of medication.
Main side effects :
- Extreme drowsiness and sluggishness
- Dry mouth, nose, and throat
- Blurred vision
- Headache
- Constipation
- Difficulty urinating
Second-Generation Antihistamines
These are newer, more advanced antihistamines introduced after the 1980s. They are designed to be minimally sedating or non-sedating, meaning they do not cause drowsiness.
This means you can take these at any time of the day and continue your work. They also have very few side effects. They are very easy to use because they only need to be taken once a day.
Commonly used examples:
- Cetirizine
- Loratadine
- Fexofenadine
- Desloratadine
Although these have much fewer side effects than the first generation, some people may experience minor side effects such as headaches and stomach upset.
So what type should I choose?
This is the most important question. The answer is, you should not decide on your own which antihistamine is best for you. You should definitely seek the advice of your family doctor (GP) or a specialist.
The reason is that the right medication for you is determined by considering a number of factors, such as your symptoms, your age, other medications you are taking, and any other medical conditions you may have (e.g., asthma, glaucoma, heart disease).
| People who should be especially careful with first-generation (drowsy) antihistamines | |
|---|---|
| People with glaucoma | Men who have difficulty urinating due to prostate enlargement |
| People with asthma or other lung diseases | People with heart disease or high blood pressure |
| People with thyroid disease | Elderly people and young children (without medical advice) |
Think about safety too.
- Do not take two types of antihistamines together without a doctor's advice.
- If you are pregnant or breastfeeding, talk to your doctor before taking any medication.
- Read the label of the medicine you are taking carefully and take only the prescribed dose.
- Do not store pills in the bathroom. The moisture and heat there can cause the medication to lose its effectiveness. Store in a cool, dry place, out of the reach of children .
- If someone accidentally takes an overdose, immediately take them to the nearest hospital Emergency Department (ETU). If necessary, call the National Poisons Information Centre at the Colombo National Hospital for advice.
Antihistamines are a very useful medication for allergic conditions, but it is very important to use them correctly and safely.
Take-Home Message
- Antihistamines work by blocking the action of histamine, which causes allergic symptoms.
- The first-generation (older) types cause severe drowsiness, while the second-generation (newer) types cause very little drowsiness.
- Always consult your doctor to determine which type of antihistamine is best for you.
- If you have other diseases (such as glaucoma, heart disease, asthma) or if you are taking other medications, it is imperative to inform your doctor.
- Never drive or do anything that requires attention when taking an antihistamine that causes drowsiness.
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