Do you also get hives when you touch a piece of dust? Or do you suddenly start itching and develop red welts? At times like these, many of us are used to going to the pharmacy and asking for an "allergy pill." Yes, these medications provide quick relief. But, how much do we really know about the medication we use, that is, antihistamines? Today, let's talk about this precisely and simply.
What is this antihistamine?
Simply put, antihistamines are a group of drugs that work against ("anti" means "against") a chemical in our body called histamine .
Now you're probably wondering what this histamine is. Histamine is a chemical messenger produced by our immune system. One of its main functions is to prepare our body to fight off something harmful, an 'allergen'. Things that can cause allergies include:
- Things in the environment: dust, pollen, pet dander, mold.
- Insect bites.
- Some foods.
- Some medications.
When something like this comes into contact with the body, histamine is activated and causes symptoms like sneezing, runny nose , itchy eyes, and body aches. So what an antihistamine does is block the action of that histamine. Not only that, these medications are also used for some stomach problems.
While many antihistamines are available over-the-counter (OTC), some require a prescription from a doctor. Also, many of the medicines we take for colds and coughs also contain antihistamines.
Are there any types of antihistamines?
Yes, there are two main types of antihistamines, depending on which histamine receptor they act on.
1. Those that block H1 receptors: These are the ones we use most often for allergies.
2. H2 receptor blockers: These are mainly used for conditions like stomach inflammation and gastritis.
H1 antihistamines - medicine for allergies
These H1 receptors are found almost everywhere in our body. In places like brain cells, respiratory tracts, and blood vessels. When these are stimulated, the allergic symptoms we talked about appear. Therefore, these symptoms are controlled with H1 antihistamines.
| When to use H1 antihistamines | |
|---|---|
| Allergic rhinitis - (Hay fever) | Frequent sneezing, runny nose. |
| Redness of the eyes (Allergic conjunctivitis) | An allergy causes red, itchy, and watery eyes. |
| Allergic skin reactions | For example: Hives, rashes, itching. |
| Vomiting and nausea | For motion sickness when traveling. |
These H1 antihistamines are again divided into two groups. Like two generations. First-generation and second-generation .
First-generation antihistamines
These are the first to be discovered, and they are a bit older. The biggest problem with these is that they cause severe drowsiness . The reason for this is that these drugs easily enter our brains. Piriton (Chlorpheniramine) is a drug that belongs to this class and we all know it.
Second-generation antihistamines
These are the newer, more advanced types. They are non-drowsy or non-drowsy, making them easy to take while working or studying. Examples of this type of medication include Cetirizine, Loratadine, and Fexofenadine.
H2 antihistamine - medicine for stomach upset
These H2 receptors are mainly found in the acid-producing cells in our stomach. That's why these H2 antihistamines are used to treat stomach problems.
- Gastritis
- GERD (chronic acid reflux) - This means that stomach acid comes up into the throat.
- Peptic ulcer disease
Medicines like Famotidine and Cimetidine belong to this category.
How should I use this medicine?
This is very important. Not all antihistamines are the same. Therefore,
- How to use the medicine: Some pills need to be taken with food. Some can be taken alone. If it's eye drops or a cream, you need to know the correct way to use it.
- Dosage: The dosage varies depending on age, weight, and type of medication. Take the amount your doctor tells you to take.
- When to take: Some are once a day. Some need to be taken multiple times a day. If you have a type that makes you sleepy, it's best to take it at night before bed.
- Duration of use: Some medications can be taken continuously, but some are only recommended for a few days.
Most importantly: The safest way is to ask your doctor what medication and dosage is right for you.
Never do these things!
- Do not double the dose. Do not take two pills at the same time to make up for a missed dose.
- Don't take medicine ahead of time.
- Do not take two types of antihistamines at the same time without medical advice.
- Do not give antihistamines for colds to children under 4 years of age without medical advice.
- Do not drive or operate machinery while taking first-generation (drowsy) antihistamines . This can cause accidents.
What are the side effects of antihistamines?
Like all medications, this one can have side effects, but they vary from person to person.
| Type of antihistamine | Possible side effects |
|---|---|
| First generation (sleepy varieties) | Severe drowsiness, dry mouth and eyes, blurred vision, dizziness, difficulty urinating. |
| Second generation (less sleepy types) | Headache, cough, sore throat, stomach ache. (High doses may cause drowsiness). |
| H2 antihistamine (for upset stomach) | These have few side effects, but some people may experience fatigue, diarrhea or constipation, and headaches. |
Risks and complications
Although it is easily available from pharmacies, this medication can be dangerous if used incorrectly. The main risk is overdose . This risk is especially high when taken with other medications, such as sedatives and sleeping pills.
Symptoms of overdose:
- Extreme drowsiness
- Seeing things that are not visible (Hallucinations)
- Restlessness (especially among children)
- Blurred vision
- Rapid heartbeat (Tachycardia)
- Seizures
If you or your child develop any of these symptoms, go to a hospital's Emergency Treatment Unit (ETU) immediately. An overdose can be fatal. If you suspect poisoning, call the National Poisons Information Centre at the Colombo National Hospital.
Also, if you have any of the following conditions, be sure to talk to your doctor before taking antihistamines.
- Diabetes
- Prostate problems (Enlarged prostate)
- Epilepsy
- Heart disease
- High blood pressure
- Glaucoma
- Thyroid problems
Is it safe during pregnancy and for nursing mothers?
If you are pregnant, trying to become pregnant, or breastfeeding, it is safest to consult your doctor before taking any medication. Although some antihistamines have been found to be safe during pregnancy, your doctor should decide what is best for you.
Take-Home Message
- Know exactly whether you are using a sleepy or non-drowsy type.
- Follow your doctor's instructions or the instructions on the medicine package. Never take more than the prescribed dose.
- Be extra careful when giving antihistamines to children and people over the age of 65. Seek medical advice.
- If you take an antihistamine that causes drowsiness, avoid driving and operating dangerous machinery.
- If you have other medical conditions, are pregnant, or are a nursing mother, be sure to talk to your doctor before taking antihistamines.
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