The Best Antihistamines

The Allergy Kit

About the Best Antihistamines


Oral antihistamines are the most commonly prescribed allergy medication. Finding the best antihistamines can sometimes be a confusing issue, since so many OTC and prescription choices are available. We attempt to clarify the differences among these drugs by providing side-by-side comparisons of some of the best antihistamines available (below).

What is an antihistamine? Simply put, it is a medication that relieves allergy symptoms by blocking histamine, the chemical “culprit” that causes many symptoms. Antihistamines are classified as H1 blockers and H2 blockers, depending on the type of receptors (on the surface of cells) that they act on. H1 receptors are associated with human tissue involving capillaries, and H2 receptors predominate in the lining of the stomach.

Even the best antihistamines do not offer anything in terms of permanent relief, nor do they relieve nasal congestion. Rather, they temporarily relieve symptoms such as: sneezing, itching, nasal drainage, and hives. Click here for an in-depth discussion about allergy symptoms, including a very useful “symptom analyzer” tool.

first generation antihistamines

The original, first generation antihistamines have drawbacks that include being short-acting, making it difficult to concentrate, and drowsiness. The major side effect of this allergy medication is drowsiness. Most of us think of histamine negatively, since we associate it with allergic reactions. However, histamine is actually a neurotransmitter which helps nerve cells communicate, thus allowing our brains to work properly. An “antihistamine,” therefore, would block the normal way our brains function.

The drug manufacturers warn patients who take this medicine to avoid activities in which they need to remain alert, such as: driving, operating machinery, and performing physically dangerous tasks. People who can not avoid these activities are advised to take this medication only at night. It is interesting to note that driving under the influence (DUI) applies to medication as well as alcohol. You can therefore be cited for DUI if you are driving while taking antihistamines!

Some of the best antihistamines that are first generation include:

• Benadryl (diphenhydramine)

• Chlor-Trimeton (chlorpheniramine)

• Atarax

• Dimetapp

• Tavist

This type of allergy medication causes several side effects. Aside from the drowsiness and inability to concentrate that we mentioned above, other side effects include: increased anxiety, nausea, loss of libido, depression, fatigue, loss of appetite, difficulty with urination, tremors, dry mouth, gastritis, and dizziness.

Despite its side effects, many doctors feel that allergy medication such as Benadryl is one of the best antihistamines available; that it is important enough to be included in every medicine chest. Since Benadryl is effective, easily absorbed, and works quickly, it is an important medication to have if there are children in your family or in case of emergency situations. Interestingly, when our good friend was bitten by a scorpion and we rushed her to the hospital, one of the first drugs they administered was benadryl.

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second generation antihistamines

The newer antihistamines, or second generation antihistamines, are thought by many to be the best antihistamines available. They are less likely to cause the drowsiness associated with the older medications, so they are often referred to as “nonsedating.” Although claritin has been recently made available over-the-counter, most of the nonsedating antihistamines require a prescription. In general, if a newer anti histamine does not work well for a patient, doctors will then resort to the original, first generation antihistamines.

The newer, second generation antihistamines include:

• zyrtec (cetirizine)

• allegra (fexofenadine)

• clarinex (desloratadine)

• claritin (loratadine)

Click here for an in-depth discussion about the best antihistamines in a range of categories.

Second Generation Antihistamines
Zyrtec Allegra Claritin Clarinex
Type of Drug Antihistamine Antihistamine Antihistamine Antihistamine
Drug is used to treat… seasonal allergic rhinitis, perennial rhinitis, hives, dust mite, mold, animal dander allergies seasonal allergic rhinitis, hives seasonal allergic rhinitis seasonal allergic rhinitis, hives
Common Side Effects sleepiness, fatigue, dizziness, headache, dry mouth, nausea nausea, diarrhea, upset stomach, headache, menstrual cramps, muscle pain, cough, dizziness headache, tiredness, feeling nervous, dry mouth, drowsiness, stomach pain, skin rash headache, nausea, diarrhea, sore throat, dry mouth, dizziness, muscle pain, menstrual cramps
Rare but serious side effects pharyngitis, abdominal pain, coughing, epistaxis, bronchospasm, vomiting fever, chills, body aches, flu-like symptoms uneven heartbeat, feeling faint, jaundice, seizures fast-uneven heartbeat, flu-like symptoms, seizure, jaundice, loss of appetite, stomach pain
How to take this medicine… Usually once daily; with full glass of water Usually twice daily, with or without food, with full glass of water Usually once daily Usually once daily, with or without food
Use caution if you take... xanax, valium, librium, restoril, halcyon, elavil, prozac, Zoloft, paxil, or any cold medicines nizoral, erythromycin, antacids, or St. John’s Wort if you have narrow angle glaucoma, peptic ulcer, prostate problems, or if you are lactating if you take other antihistamines, aphthasol, or if you are pregnant
FDA pregnancy category Category B: unlikely to harm an unborn baby Category C: may be harmful to on unborn baby Category B: unlikely to harm an unborn baby Category C: may be harmful to an unborn baby

The Allergy Kit

the best antihistamines-third generation

As you are aware by now, first generation antihistamines can potentially cause problems because of their tendency to cause sedation. Second generation antihistamines such as loratadine and cetirizine were developed in the early 1980s, and they provided a distinct benefit in that they did not cause the antihistamine side-effects of sedation, among others. A problem developed, however, when some of these newer drugs were found to cause cardiac problems.

Third generation antihistamines may soon be the best antihistamines for many patients. They are now being developed in order to eliminate the possibility of cardiac toxicity. One of the first of these, fexofenadine, was approved in July of 1996, and more third generation antihistamines are under development.