1. Health

Your suggestion is on its way!

An email with a link to:


was emailed to:

Thanks for sharing About.com with others!

Most Emailed Articles

Worst Ways To Handle Conflict

Allergic Rhinitis (Hay Fever and Rose Fever) and Chronic Nasal Congestion


An in-depth report on the causes, diagnosis, treatment, and prevention of common nasal allergies.

Alternative Names

Decongestants; Hay Fever; Rhinitis


Histamine is one of the chemicals released when antibodies overreact to allergens and is the cause of many symptoms of allergic rhinitis. Antihistamines have the following benefits:

  • They relieve itching, sneezing, and nasal discharge.
  • They also relieve other allergy symptoms unrelated to rhinitis, including hives and some rashes.
  • Some of the newer antihistamines, such as etirizine (Zyrtec) and desloratadine (Clarinex), relieve nasal congestion.

Experts recommend that patients take them before an anticipated allergy attack if possible.

Many antihistamines are available and include short-acting and long-acting forms. They are available in tablet, nasal-inhaler, eye drop, and syrup form. Antihistamines are generally categorized as first- and second-generation, which generally are based on whether they have ingredients that cause greater or lesser sedation.

There are some notes of caution when taking any generation antihistamine:

  • Antihistamines may thicken mucus secretions and can actually worsen bacterial sinusitis. People with bacterial rhinitis or sinusitis should not use antihistamines, even during allergy season.
  • Antihistamines can lose their effectiveness over time and a different one may need to be tried.

First-Generation Antihistamines

First-Generation Antihistamines Ingredients and Brand Names. The older, so-called first generation antihistamines include:

  • Diphenhydramine (Benadryl).
  • Carbinoxamine (Clistin).
  • Clemastine (Tavist).
  • Chlorpheniramine (Chlor-Trimeton). Some health professionals recommend this agent if antihistamines are required during pregnancy. And many believe it is as effective as the second generation antihistamines and much less expensive.
  • Brompheniramine (Dimetane).

First-generation antihistamines contain compounds called anticholinergics, which tend to produce the side effects that differentiate this group from second-generation antihistamines.

Side Effects.

  • Drowsiness and impaired thinking.
  • Dry mouth.
  • Dizziness.
  • Agitation.
  • Insomnia or nightmares.
  • Sore throat.
  • Rapid heart beat and chest tightness (uncommon and should be reported).
  • Men with enlarged prostate glands may experience difficulty urinating.

Further Notes on Drowsiness from First-Generation Antihistamines. Drowsiness is the most distressing side effect reported from first-generation antihistamines, and is potentially serious. Some evidence indicates this effect poses a higher than average risk for work-related and automobile accidents than alcohol, narcotics, or prescription sedatives. Of interest, however, was a 2001 study suggesting that first-generation antihistamines do not have the same effect on children. In the study, children who took Benadryl had no greater impairment of alertness or learning than children who took loratadine (Claritin), one of the common second-generation antihistamines, which are supposed to cause less sleepiness. In fact, a major 2003 analysis could find no strong differences in effects on sedation in general between the first- and second-generation antihistamines.Still, experts caution against the first-generation antihistamines for people most at risk from sedative effects, particularly elderly individuals.

To offset the sedative effect, the following tips may be helpful:

  • Take at home a few hours before bedtime.
  • Avoid alcohol and tranquilizers, which increase drowsiness.
  • Avoid driving or operating heavy machinery.

It should be noted that sedation lessens over time.

Second-Generation (Nonsedating) Antihistamines

The newer second-generation antihistamines do not contain anticholinergics and so do not usually cause drowsiness to the extent that the first generation antihistamines do. They are then sometimes referred to collectively as nonsedating antihistamines.

Of note, a major 2003 analysis reported that although Benedryl, the most common first-generation antihistamine, had a more negative effect on daily activities than the newer antihistamines, they differences were modest. Researchers in the study concluded that no clear distinction exists between the first- and second-generation antihistamines. In addition, the newer agents are also more expensive, since most require a prescription. (As many become available of the counter, costs should drop.)

Brand Names. The second-generation agents include the following:

  • Loratadine (Claritin). Claritin is available over the counter and is approved for children age two and over. Desloratadine (Clarinex) is similar to Claritin but significantly more potent and longer lasting. It is available only by prescription.
  • Cetirizine (Zyrtec). Zyrtec is approved for both indoor and outdoor allergies. It is the only antihistamine to date approved for infants as young as six months.
  • Fexofenadine (Allegra).
  • Acrivastine (Semprex).
  • Ebastine, norastemizole, levocetirizine, and mizolastine are other promising and unique second-generation antihistamines under investigation in the US and Europe. Some may prove to be useful for special populations.

The FDA has ruled that Allegra, Claritin, and Zyrtec are safe for over-the-counter use, with Claritin the first to be approved. Studies suggest that cetirizine (Zyrtec) is more effective than either of these other agents in improving symptoms, including in children, although cetirizine causes more drowsiness at higher doses. One 2001 comparison study suggested that Claritin was more effective than Allegra in improving symptoms in a shorter period of time.

Zyrtec and Claritin are approved for those under five years of age, although most appear to be safe in children. Zyrtec is the only antihistamine approved for both indoor and outdoor allergies and for infants as young as six months. Both are available in syrup form. Studies with Zyrtec have reported fewer symptoms in children allergic to dust mites, and a 2002 study reported that infants with allergies who were given Zyrtec were much less likely to develop asthma later on than untreated infants. Claritin at this time is generally the preferred agent for young people, however, because it has the least negative effect on concentration and learning. Women who are pregnant or nursing should avoid these medications unless recommended by a physician.

Side Effects and Precautions.

  • Common side effects may include headache, dry mouth, and dry nose. (These are often only temporary and go away during treatment.)
  • Drowsiness can occur in over 10% of adults and between 2% and 4% of children.
  • Uncommon side effects include rapid heart beat and chest tightness and should be reported.
  • Extended-release forms of Claritin and Zyrtec have other ingredients that cause other symptoms, including nervousness, restlessness, and insomnia. Some patients taking Claritin-D 24 Hour Extended Release tablets have reported obstruction in the upper gastrointestinal tract, including difficulty swallowing. It is not known if this is common or typical of all second-generation agents.

Drug and Food Interactions. Two earlier second generation drugs, terfenadine (Seldane) and astemizole (Hismanal), in rare cases, caused dangerous heart rhythm abnormalities, particularly in high doses or in people who have liver disease or are taking certain other medications or ingesting grapefruit juice. Both Seldane and Hismanal have been taken off the market. Allegra, Zyrtec, and Claritin do not appear to pose any of the dangers associated with Seldane.

Until more is known, anyone who takes a second-generation antihistamine, though, should probably avoid or use with caution combinations with grapefruit juice or the drugs that caused problems with Seldane and Hismanal. Such medications include the following:

  • The antibiotics clarithromycin (Biaxin) and troleandomycin.
  • Certain HIV protease inhibitors.
  • The antidepressants serotonin-reuptake inhibitors (e.g., Prozac, Paxil, and Serzone).

Nasal-Spray Antihistamines

Azelastine (Astelin) and levocabastine (Livostin) are available in nasal spray form. They can reduce nasal congestion as well as allergy symptoms. Both reduce symptoms, although azelastine may be more effective in some patients. Their disadvantages are a bitter taste, drowsiness, and expense. They are not as effective as steroid nasal sprays.

Combination Antihistamines and Decongestants

Many prescription and non-prescription products that combine antihistamines and decongestants are available. A small sample of these combinations sold over the counter includes Allerest, Sudafed Severe Cold Formula, Vicks DayQuil, Benadryl Allergy/Sinus, Contac Day/Night Allergy & Sinus. Prescription combinations include Claritin-D, Allegra D, and Zyrtec-D. They may be effective for all symptoms within 60 minutes, with congestion clearing up first. As a rule, children should not be given combination remedies, which can cause headaches, agitation, and loss of appetite.


©2014 About.com. All rights reserved.