Antihistamines: What They Are and When to Take Them

ANTIHISTAMINES

- antihistamines They are effective drugs against allergies, as they block or antagonize the effects of thehistamine, a chemical released by the body during an allergic reaction.

Using an antihistamine can be useful for both seasonal allergies both for the food, but in some cases, also for the dust allergies.

However, these medicines are often wasted because they are taken when they are not needed or in the wrong doses. It is also important to know that antihistamines have limited effects over time and they are not conclusive.

WHAT IS HISTAMINE?

Histamine is abiogenic amine, which acts as a chemical mediator of inflammation. This organic molecule plays a crucial role in immune responses and binds to specific receptors in the body to exert its functions.

TYPES OF HISTAMINE RECEPTORS

• H1: Located mainly in the heart, central nervous system, and vascular smooth muscle. They are also present in the eyes, respiratory tract, and skin. These receptors are involved in regulating vascular dilation and capillary permeability, influencing symptoms such as: redness, swelling e pruritus.
• H2Found predominantly in the heart, central nervous system, and stomach, they play a key role in regulating gastric acid secretion, which is essential for digestion.
• H3: Present mainly in the central nervous system, but also in the intestines, stomach, and lungs. These receptors modulate the release of neurotransmitters and are involved in controlling appetite and sleep.
• H4: Found in the bone marrow and spleen, these receptors are important in modulating immune responses and inflammation.

WHEN TO TAKE ANTIHISTAMINES

Antihistamines are useful for mitigate the symptoms of allergic reactions, acting against symptoms such as:

• Tearing
• Sneezing
• Nasal discharge
• itch (palate, eyelids, nose)
• Skin rashes

It should be noted, however, that antihistamines are not always able to control all the possible symptoms of an allergic reaction. For example, if you have a nasal congestion, your doctor may recommend a decongestant. Therefore, an antihistamine isn't always the best solution for allergies, and here's why.

WHEN THEY ARE USELESS

Antihistamines are essential tools in the treatment of allergic reactions, but there are situations in which these drugs are ineffective or unsuitable. Here are some examples:

• Upper respiratory tract infectionsAntihistamines are not effective in treating symptoms caused by viruses, such as the common cold. These symptoms, although they include runny nose and sneezing, are not mediated by histamine, making antihistamines useless in these cases.
• AsthmaAlthough antihistamines can relieve some allergic symptoms that can worsen asthma (such as a runny nose or itching), they are not effective treatments for asthma itself. Asthma requires specific medications that relax the muscles in the airways or reduce inflammation in the lungs.
• Non-allergic skin diseases: Conditions such as the Psoriasis or eczema are not caused by a histamine-mediated allergic reaction. Therefore, antihistamines are generally ineffective in treating the inflammation and itching associated with these skin conditions.
• Some types of food allergies: although in some cases antihistamines can help manage mild allergic reactions to foods, they are not suitable for treating serious allergic reactions such as anaphylaxis, which can be life-threatening and require the immediate use of epinephrine.
• Chronic non-histamine-mediated allergiesSome chronic conditions, such as nonallergic rhinitis, are not affected by histamine and therefore do not respond to antihistamines.

HOW TO TAKE ANTIHISTAMINES

Antihistamines, like any other drug, must be used scrupulously following medical indications about doses e frequency of intakeIt is essential to consult a doctor or pharmacist for precise instructions, or carefully read the package leaflet included with the medicine, which provides details on how to take the drug, the recommended dosage, and potential side effects.

Before taking an antihistamine, consider the following:

• Method of recruitment: Check whether the medicine should be taken with water and on a full stomach, especially if it is a pill.
• Correct application: Use topical or nasal products, such as sprays or drops, with caution.
• Dosing: Be sure to adjust the dose based on your weight and age, following your doctor's instructions.
• Frequency and duration: Respect the prescribed times of intake. Older generation antihistamines, for example, are often recommended for the evening, before sleeping.
• Administration timeFollow the prescribed duration of treatment, which may vary depending on the type of antihistamine. Some can be taken long-term, others only for short periods. Always seek the advice of a specialist.

DOSAGES

The dosage of antihistamines depends on the type being used. There are numerous types of antihistamines on the market that can be administered via:

• Injection with syringe
• Oral
• Application cutaneous (creams or gels)
• Nasal (spray)
• Administration eye (eye drops)

Based on the type of drug Daily doses and duration of administration vary depending on the individual patient's condition. The antihistamine's effects are noticeable after about 30 minutes and are fully effective after 2 hours. Current products, with a single dose, can be effective for up to 24 hours.

In any case, depending on the medication, it's a good idea to ask your doctor or pharmacist for advice. For over-the-counter antihistamines, it's important to: read the package leaflet.

MOST COMMON ANTIHISTAMINES

The most common antihistamines used in Italy include several active ingredients that can be administered in different forms such as tablets, nasal spray, eye drops, and cream. Here's a list of the main antihistamines you might find:

• Carbinoxamine
• Terfenadine
• Cyclizine
• Mizolastine
• Cyproheptadine
• Chlorpheniramine
• Oxatomide
• Naphazoline
• Diphenhydramine
• Phenoxyphenadine
• Hydroxyzine
• Ketotifen
• Levocetirizine
• Meclizine

SIDE EFFECTS

Antihistamines, like all medications, can cause side effects. Their incidence and severity can vary depending on the drug generation. It is essential to be informed to effectively manage these effects.

• Drowsiness: Older antihistamines often cause significant drowsiness, which may impair the ability to drive or operate machinery.
• Dry mouthThis effect is common and can be annoying but manageable.
• Blurred vision and urinary retentionOther possible side effects include difficulty with visual accommodation and problems emptying the bladder.
• Headache: A common but generally mild side effect.
• MalaiseA feeling of general discomfort may occasionally accompany the use of these drugs.
• Less drowsinessCompared to their predecessors, second-generation antihistamines are less likely to cause drowsiness, making them safer for daytime use.

WHAT TO KNOW ABOUT ALLERGIES:

• How to distinguish a cold from an allergy
• What to do about dog and cat allergies?
• Children's Allergies: Symptoms and Prevention
• Food allergies: causes, remedies, and prevention