Antihistamine facts for kids
Quick facts for kids Antihistamine |
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|---|---|
| Drug class | |
The chemical structure of histamine
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| Class identifiers | |
| ATC code | R06 |
| Mechanism of action | • Receptor antagonist • Inverse agonist |
| Biological target | Histamine receptors • HRH1 • HRH2 • HRH3 • HRH4 |
| External links | |
| MeSH | D006633 |
| Legal status | |
Antihistamines are a type of medicine used to treat allergies, such as allergic rhinitis (hay fever), and the common cold. Many people take antihistamines to get relief from symptoms like a stuffy nose, sneezing, or itchy skin rashes called hives. These symptoms are often caused by things like pollen, dust mites, or pet dander.
Antihistamines are usually taken for a short time. Most can be bought over-the-counter, which means you don't need a prescription from a doctor. However, it's always a good idea to talk with a parent or a doctor before taking any new medicine, especially if you need it for a long time.
The name "antihistamine" gives a clue about how it works. These medicines work against a chemical in your body called histamine. Scientists group antihistamines into different classes based on which histamine signals, or histamine receptors, they block. The two most common types are H1-antihistamines and H2-antihistamines.
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How Do Antihistamines Work?
Your body makes a chemical called histamine as part of its immune system. You can think of histamine as a security guard. When it detects something it thinks is harmful, like a virus, it triggers a response to get rid of it.
Sometimes, histamine can overreact to harmless things like pollen or dust. This overreaction is what we call an allergic reaction. Histamine causes blood vessels to widen and become more leaky. This lets fluid escape into the nearby tissues, leading to a runny nose, watery eyes, sneezing, and itching.
Antihistamines work by blocking histamine from connecting with its receptors in your body's cells. By blocking these signals, antihistamines stop the allergic reaction and help relieve the uncomfortable symptoms.
Main Types of Antihistamines
There are several types of antihistamines, but they mainly fall into two groups that people use for different reasons.
H1 Antihistamines: For Allergies
H1-antihistamines are the most common type and are used to treat allergy symptoms. They work by blocking the H1 receptors, which are found all over the body. These are the medicines you would likely take for hay fever, hives, or other common allergies. There are two generations of H1-antihistamines.
First-Generation Antihistamines
These were the first type of antihistamines developed. They are very effective at treating allergies, but they often have a side effect of making people feel sleepy. This is because they can travel into the brain and affect the receptors there.
- Examples include: Diphenhydramine (Benadryl) and Chlorpheniramine.
Second-Generation Antihistamines
These are newer antihistamines that were designed to reduce the side effect of drowsiness. They mostly work on receptors outside of the brain, so they are less likely to make you feel tired. These are often a popular choice for people who need to stay alert at school or work.
- Examples include: Loratadine (Claritin), Cetirizine (Zyrtec), and Fexofenadine (Allegra).
H2 Antihistamines: For Stomach Problems
H2-antihistamines work on a different receptor, the H2 receptor. These receptors are mainly found in the lining of the stomach. When histamine connects with these receptors, it tells the stomach to produce more acid.
Too much stomach acid can cause problems like acid reflux (heartburn) or peptic ulcers. H2-antihistamines reduce the amount of acid your stomach makes, which helps to relieve these conditions.
- Examples include: Famotidine (Pepcid) and Cimetidine.
A Brief History of Antihistamines
Scientists first discovered compounds with antihistamine effects in the 1930s. The first antihistamine that was safe for people to use, called Phenbenzamine, became available in 1942. This was a major breakthrough for treating allergies.
Over the next decade, many more "first-generation" antihistamines were developed, like Diphenhydramine (Benadryl). While helpful, their sleepy side effects were a problem for many people.
In the 1970s, researchers developed the first "second-generation" antihistamine, terfenadine. This led to the creation of the non-drowsy allergy medicines that are very common today, such as loratadine (Claritin) and fexofenadine (Allegra). This research also helped scientists better understand how histamine works, leading to the development of H2-antihistamines for stomach issues.
Important Safety Information
Most people can take antihistamines safely, but it's important to remember that they are medicine.
- Always follow the instructions on the label or given by a doctor.
- Some antihistamines, especially the first-generation ones, can cause drowsiness. You should be careful about activities like riding a bike until you know how the medicine affects you.
- It is best to talk with a parent, guardian, or doctor before taking an antihistamine. This is especially important if you have other health conditions or are taking other medicines.
- Older adults may be more sensitive to side effects like drowsiness.
See also
- Antileukotriene
- Immunotherapy
