Some of the antihistamine formulations that are often used to treat colds and the flu include:

• Antihistamine/decongestant combinations. These drugs are used to treat a stuffy nose, runny nose and sneezing. The antihistamines in these drugs prevent the effects of histamines released by the body that trigger certain symptoms. Decongestants narrow the blood vessels, lessening nasal congestion.
  
  
• Antihistamine/decongestant/analgesic combination. These drugs provide the same treatment response as antihistamine/decongestant combinations, but also add an analgesic that helps relieve fever, headache, and aches and pains associated with colds and the flu.
  
  
• Antihistamine/decongestant/anticholinergic combinations. These drugs provide the same treatment response as antihistamine/decongestant combinations, but also add an anticholinergic (an antispasmodic drug) that produces a drying effect in the nose and chest and helps open the airways.

Patients who wish to purchase antihistamine and decongestant combinations that contain the drug pseudoephedrine will need to speak with a pharmacist, show a form of identification and sign a logbook. In addition, any antihistamine/decongestant combinations that contain the ingredient phenylpropanolamine have been found to be unsafe by the U.S. Food and Drug Administration. Patients with old medications at home that contain this ingredient are encouraged to dispose of those medications.

Antihistamines may also be found in medications formulated to treat coughing, such as antitussives (cough suppressants) or expectorants (which stimulate coughing to expel excess mucus).

Some common antihistamine medications include:

Some common antihistamine/decongestant combinations include:

Some common antihistamine/decongestant/analgesic combinations include:

Some common antihistamine/decongestant/anticholinergic combinations include:

Antihistamines used to treat colds most often are administered though tablets, liquids or nasal sprays.

Antihistamines can also be divided into the following groups:

• H1 antihistamines. These antihistamines are used to block H1 receptors present in many types of tissue (including the small blood vessels known as capillaries), and help to prevent an allergic response. Because H1 receptors are the most common type of receptor, this is the most common and frequently used form of antihistamine.
  
  
• Nonsedating antihistamines. Because of the sleepiness experienced by almost half of all patients taking early forms of antihistamines, nonsedating (non-drowsy) forms of the medication were developed. Although early forms of nonsedating antihistamines were found to be unsafe, newer types (e.g., loratadine and fexofenadine) are considered both safe and effective. The early, unsafe types of antihistamines have been removed from the market in the United States.
  
  
• Lightly sedating antihistamines. Some forms of newer antihistamines are occasionally found to cause sedation in people who use them. For this reason, the FDA has decided that these forms of antihistamines, such as cetirizine, should be called “lightly sedating” instead of “nonsedating.”