Skip to Content

Antihistamines

Written on February 14, 2018 by C. Fookes, BPharm

Medically reviewed on February 14, 2018 by C. Fookes, BPharm

What are Antihistamines?

Antihistamines are a class of agents that block histamine release from histamine-1 receptors and are mostly used to treat allergies or cold and flu symptoms, although some first-generation antihistamines may also be used for other conditions.

Histamine-1 receptors are located in the airways, blood vessels and gastrointestinal tract (stomach and esophagus). Histamine-1 receptors are also found in the brain and spinal cord.

What are antihistamines used for?

Antihistamines are very good at relieving symptoms of an allergic reaction, such as:

  • edema (swelling)
  • inflammation (redness)
  • itch
  • rash
  • red and watery eyes
  • runny nose
  • sneezing.

This makes antihistamines very effective in the treatment of:

First generation antihistamines (see explanation below) also act in the brain and spinal cord, and on other receptors. This makes some of them also useful for:

  • inducing sleep
  • preventing or treating motion sickness
  • reducing anxiety
  • in people with Parkinson’s disease unable to tolerate more potent agents.

What are the differences between antihistamines?

Antihistamines can be classified into two main categories:

  • first-generation antihistamines
  • second-generation antihistamines.

First-generation antihistamines were developed more than seventy years ago and are still in widespread use today. They act on histamine receptors in the brain and spinal cord and in the rest of the body (called the periphery). They also act on muscarinic, alpha-adrenergic, and serotonin receptors. This means that first-generation antihistamines are more likely to cause side effects such as sedation, dry mouth, dizziness, low blood pressure, and a rapid heart-beat. They are also more likely than second-generation antihistamines to impair a person’s ability to drive or operate machinery. Interactions with other drugs are more common with first-generation antihistamines compared with second-generation antihistamines.

Second generation antihistamines were developed in the 1980s and are much less sedating than first-generation antihistamines. They act on histamine-1 receptors in the periphery and are unlikely to penetrate the brain, so are less likely to cause side effects or interact with drugs. Most second-generation antihistamines do not cause drowsiness, although some (such as cetirizine and fexofenadine), may be more likely to do so at higher dosages.

Common antihistamines available in the U.S.

First Generation Antihistamines

Second Generation Antihistamines

What are the side effects of antihistamines?

Side effects of first-generation antihistamines may include:

  • abdominal pain
  • blurred or double vision
  • constipation
  • dry eyes
  • a dry mouth
  • drowsiness or sedation
  • a headache
  • low blood pressure
  • mucus thickening in the airways
  • a rapid heart beat
  • urinary problems

Side effects of second generation antihistamines are uncommon but may include:

List of Antihistamines:

Filter by:
Drug NameView by: Brand | Generic Reviews Avg. Ratings
Allegra ODT
generic name: fexofenadine
1 review
   
10
Aller-Tec
generic name: cetirizine
1 review
   
10
Seldane
generic name: terfenadine
3 reviews
   
10
Zymine
generic name: triprolidine
1 review
   
9.7
Chlor-Trimeton (Pro)
generic name: chlorpheniramine
12 reviews
   
9.1
All Day Allergy (Pro)
generic name: cetirizine
1 review
   
9.0
Compoz Nighttime Sleep Aid
generic name: diphenhydramine
2 reviews
   
9.0
Palgic (Pro)
generic name: carbinoxamine
2 reviews
   
9.0
Q-Dryl
generic name: diphenhydramine
1 review
   
9.0
Unisom SleepMelts
generic name: diphenhydramine
1 review
   
9.0
Wal-finate
generic name: chlorpheniramine
1 review
   
9.0
Promethegan (Pro)
generic name: promethazine
1 review
   
8.4
Children's Claritin Allergy
generic name: loratadine
3 reviews
   
8.3
Phenergan (Pro)
generic name: promethazine
87 reviews
   
8.3
Benadryl Children's Allergy
generic name: diphenhydramine
0 reviews
   
8.0
Antinaus 50
generic name: promethazine
0 reviews
   
7.7
Benadryl (Pro)
generic name: diphenhydramine
50 reviews
   
7.6
Clarinex (Pro)
generic name: desloratadine
5 reviews
   
7.5
Benadryl Allergy
generic name: diphenhydramine
26 reviews
   
7.4
Allegra (Pro)
generic name: fexofenadine
69 reviews
   
7.3
Zyrtec (Pro)
generic name: cetirizine
114 reviews
   
7.2
Allerhist-1
generic name: clemastine
0 reviews
   
7.0
Banophen
generic name: diphenhydramine
0 reviews
   
7.0
Polaramine
generic name: dexchlorpheniramine
3 reviews
   
7.0
Sominex
generic name: diphenhydramine
27 reviews
   
6.9
Atarax (Pro)
generic name: hydroxyzine
97 reviews
   
6.5
Phenadoz (Pro)
generic name: promethazine
0 reviews
   
6.5
Xyzal (Pro)
generic name: levocetirizine
186 reviews
   
6.3
Lodrane 12 Hour
generic name: brompheniramine
0 reviews
   
6.0
Vistaril (Pro)
generic name: hydroxyzine
175 reviews
   
5.9
Alavert (Pro)
generic name: loratadine
1 review
   
5.5
Hyzine
generic name: hydroxyzine
2 reviews
   
5.5
Simply Sleep
generic name: diphenhydramine
14 reviews
   
5.4
Unisom SleepGels
generic name: diphenhydramine
14 reviews
   
5.4
Claritin (Pro)
generic name: loratadine
19 reviews
   
5.0
Nytol
generic name: diphenhydramine
8 reviews
   
4.7
Triaminic Thin Strips Cough & Runny Nose
generic name: diphenhydramine
0 reviews
   
3.0
Allegra Allergy
generic name: fexofenadine
6 reviews
   
2.9
Aller-Ease
generic name: fexofenadine
1 review
   
1.0
Vicks QlearQuil Nighttime Allergy Relief
generic name: diphenhydramine
1 review
   
1.0
12 Hour Allergy Relief
generic name: clemastine
0 reviewsAdd rating
Ala-Hist IR
generic name: dexbrompheniramine
0 reviewsAdd rating
All Day Allergy Children's (Pro)
generic name: cetirizine
0 reviewsAdd rating
Aller-Chlor
generic name: chlorpheniramine
0 reviewsAdd rating
Aller-Tec Children's
generic name: cetirizine
0 reviewsAdd rating
Allergy Relief
generic name: chlorpheniramine
0 reviewsAdd rating
Allergy Relief 24 Hour
generic name: loratadine
0 reviewsAdd rating
Allergy Relief Tablets
generic name: loratadine
0 reviewsAdd rating
Allermax
generic name: diphenhydramine
0 reviewsAdd rating
Arbinoxa (Pro)
generic name: carbinoxamine
0 reviewsAdd rating
Bactimicina Allergy
generic name: loratadine
0 reviewsAdd rating
Bromax (Pro)
generic name: brompheniramine
0 reviewsAdd rating
Brovex CT
generic name: brompheniramine
0 reviewsAdd rating
C.P.M.
generic name: chlorpheniramine
0 reviewsAdd rating
Carboxine
generic name: carbinoxamine
0 reviewsAdd rating
Children's Allergy Relief
generic name: cetirizine
0 reviewsAdd rating
Children's Allergy Relief 24 Hour
generic name: loratadine
0 reviewsAdd rating
Chlo-Amine
generic name: chlorpheniramine
0 reviewsAdd rating
Chlor-Mal
generic name: chlorpheniramine
0 reviewsAdd rating
ChlorTan
generic name: chlorpheniramine
0 reviewsAdd rating
Clarinex Reditabs
generic name: desloratadine
0 reviewsAdd rating
Claritin Reditabs
generic name: loratadine
0 reviewsAdd rating
Clear-Atadine
generic name: loratadine
0 reviewsAdd rating
Complete Allergy Relief
generic name: diphenhydramine
0 reviewsAdd rating
Dayhist Allergy
generic name: clemastine
0 reviewsAdd rating
Dicopanol
generic name: diphenhydramine
0 reviewsAdd rating
Dimetane Extentab
generic name: brompheniramine
0 reviewsAdd rating
Dimetapp Children's ND Non-Drowsy Allergy (Pro)
generic name: loratadine
0 reviewsAdd rating
Diphedryl
generic name: diphenhydramine
0 reviewsAdd rating
Diphenhist
generic name: diphenhydramine
0 reviewsAdd rating
Dytuss
generic name: diphenhydramine
0 reviewsAdd rating
Ed-Chlortan
generic name: chlorpheniramine
0 reviewsAdd rating
Ed ChlorPed
generic name: chlorpheniramine
0 reviewsAdd rating
Ed Chlor Ped Jr.
generic name: chlorpheniramine
0 reviewsAdd rating
Histex CT
generic name: carbinoxamine
0 reviewsAdd rating
Histex IE
generic name: carbinoxamine
0 reviewsAdd rating
Histex PD
generic name: carbinoxamine
0 reviewsAdd rating
Histex PD Drops
generic name: triprolidine
0 reviewsAdd rating
Histex Syrup
generic name: triprolidine
0 reviewsAdd rating
J-Tan PD
generic name: brompheniramine
0 reviewsAdd rating
Karbinal ER (Pro)
generic name: carbinoxamine
0 reviewsAdd rating
Leader Allerhist
generic name: clemastine
0 reviewsAdd rating
LoHist-12
generic name: brompheniramine
0 reviewsAdd rating
M-Hist PD
generic name: triprolidine
0 reviewsAdd rating
ohm Allergy Relief
generic name: loratadine
0 reviewsAdd rating
PediaCare Children's Allergy
generic name: diphenhydramine
0 reviewsAdd rating
PediaTan
generic name: chlorpheniramine
0 reviewsAdd rating
Pediatex
generic name: carbinoxamine
0 reviewsAdd rating
Pediox
generic name: carbinoxamine
0 reviewsAdd rating
Polmon
generic name: dexchlorpheniramine
0 reviewsAdd rating
Quenalin
generic name: diphenhydramine
0 reviewsAdd rating
Ryvent (Pro)
generic name: carbinoxamine
0 reviewsAdd rating
Scot-Tussin Allergy
generic name: diphenhydramine
0 reviewsAdd rating
Siladryl Allergy
generic name: diphenhydramine
0 reviewsAdd rating
Silphen Cough
generic name: diphenhydramine
0 reviewsAdd rating
Siltane
generic name: brompheniramine
0 reviewsAdd rating
Sleepinal
generic name: diphenhydramine
0 reviewsAdd rating
Tavist-1
generic name: clemastine
0 reviewsAdd rating
Tavist Allergy
generic name: clemastine
0 reviewsAdd rating
Tavist ND
generic name: loratadine
0 reviewsAdd rating
Topco Allergy
generic name: chlorpheniramine
0 reviewsAdd rating
Tranquil Nighttime Sleep Aid
generic name: diphenhydramine
0 reviewsAdd rating
Tripohist
generic name: triprolidine
0 reviewsAdd rating
Twilite
generic name: diphenhydramine
0 reviewsAdd rating
Valu-Dryl
generic name: diphenhydramine
0 reviewsAdd rating
Vanaclear PD
generic name: triprolidine
0 reviewsAdd rating
Vanahist PD
generic name: triprolidine
0 reviewsAdd rating
VaZol
generic name: brompheniramine
0 reviewsAdd rating
Vicks QlearQuil All Day & All Night 24 Hour Allergy Relief
generic name: loratadine
0 reviewsAdd rating
Wal-itin
generic name: loratadine
0 reviewsAdd rating

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Hide