Do you also start sneezing, have red eyes, and runny noses as soon as you touch a speck of dust or eat something? Sometimes you may even scratch your entire body. When you have an allergy like this, or as we call it, an allergy, many of us run to find an antihistamine pill. So, today we will find out exactly what this is, how it works, and what precautions you should take while using it.
What exactly is an antihistamine?
Simply put, when something we are allergic to, such as dust, pollen, animal dander, or certain foods, enters our body, our body produces a chemical called 'histamine.' Imagine this, like our body's defense system sounding an 'alarm' that an enemy has arrived.
It's when this chemical called histamine is released that we get those allergic symptoms. That is:
- Sneezing
- Runny nose and eyes
- Itchy eyes, nose, throat, and skin
- Red welts on the skin (we also call them hives)
So, what antihistamines do is reduce the activity of that chemical called histamine, or block it completely. Then those allergic symptoms gradually decrease and you get relief.
How long does it take for the medicine to work? Is it better to take it early?
Most of us take medicine when we have an allergic reaction, meaning when our nose is blocked and our eyes are watering. Usually, an over-the-counter (OTC) or prescription antihistamine starts working within 30 minutes. It takes an hour or two for the full effect to kick in.
However, doctors say that it is much better to take medication before symptoms appear, rather than waiting for them to appear. We call this 'Allergy Pretreatment' .
Do you know why? If you wait until the symptoms are severe, a simple medication may not be enough to control them. You may need more powerful medications.
Imagine that you get allergies every year during the Sinhala New Year due to dust. So, you can start taking an antihistamine daily about two weeks before that time. Then you can prevent the allergies from coming or make them come and go very rarely. The most important thing is to continue using the medicine until the doctor tells you to, even if you feel better. If you stop, the symptoms may reappear.
Types of antihistamines and choosing the right one for you
Antihistamines can be divided into two main types. It is very important for you to know the main difference between these two.
| Type of antihistamine | Main feature | Examples (common names in Sri Lanka) |
|---|---|---|
| First-generation | These can cause significant drowsiness . Therefore, they are not suitable for driving or operating machinery. It is best to use them at night. | Chlorpheniramine (known to many as 'Piriton'), Diphenhydramine , Hydroxyzine |
| Second-generation | These do not cause drowsiness or cause very little drowsiness. They can be used safely even during the day. | Cetirizine , Loratadine , Fexofenadine , Levocetirizine , Desloratadine |
Which one is best for you?
In general, it is best to choose a second-generation medication that is less sleepy so that it does not interfere with your daily activities. These work for a longer period of time, such as 12 or 24 hours, so you can take one pill a day. However, if you have allergies and difficulty sleeping at night, your doctor may recommend that you take a first-generation medication that is less sleepy at night.
These medications come in the form of tablets, capsules, syrups, nasal sprays, and eye drops.
Side effects of antihistamines and things to be aware of
Like any medication, antihistamines can have minor side effects . Side effects are most commonly seen with the first-generation medications that we mentioned earlier, which cause drowsiness.
Common side effects include:
- Dry mouth and throat
- Sleepiness (the main thing)
- Dizziness
- Nausea and vomiting
- Difficulty urinating
- Slightly blurred vision
- Confusion (especially in the elderly)
- Some children have insomnia or hyperactivity.
Definitely take care!
Most importantly: Never start using this medication without talking to your doctor about any other illnesses you may have or other medications you are taking.
- Driving: If you take a medication that makes you sleepy, do not drive or operate machinery for any reason.
- Alcohol: Taking alcohol with antihistamines can greatly increase drowsiness and dizziness, so avoid it completely.
- Other medical conditions: Be sure to tell your doctor if you have conditions such as an enlarged prostate, heart disease, high blood pressure, thyroid problems, liver or kidney disease, or glaucoma.
- Pregnant and nursing mothers: If you are pregnant or nursing, do not take any medication without consulting your doctor. Although some antihistamines are said to be safe, use them only under medical advice.
- For young children: Do not give first-generation (drowsy) antihistamines to children under 2 years of age. If you are giving any medicine to a child, consult a pediatrician and be sure to know the correct dosage.
In conclusion, antihistamines are a very effective treatment for allergies. But the most important thing is to use them correctly, as appropriate for you, and as directed by your doctor.
Take-Home Message
- Antihistamines are a type of medication that controls allergy symptoms. They work by blocking a chemical in the body called histamine.
- Starting medication before allergy symptoms appear (e.g., a few weeks before the start of a dusty season) can provide great relief.
- Second-generation antihistamines (e.g., Cetirizine, Loratadine) that do not cause drowsiness are best used during the day.
- These are not very useful for nasal congestion. For that, other sprays or medications may be needed as directed by a doctor.
- Be sure to talk to your doctor before using any antihistamine, especially if you have other medical conditions, are pregnant, or are taking other medications.
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