Definition of Antihistamine

Antihistamines are a class of drugs used primarily to deal with allergic reactions, although there are other situations when physicians prescribe them. Both prescription and over-the-counter versions are available under a wide variety of brand names. Consider antihistamines as well as other types of drugs when fighting an allergy.

Function

Take an antihistamine to counteract histamine--a substance produced by the body in response to certain triggers, such as allergens or irritants. Other functions of antihistamines include combating motion sickness, relieving nausea and anxiety and using the sedative effect to aid sleep. Some Parkinson's patients may find relief from stiffness and tremors with antihistamines, according to the staff of the Mayo Clinic.

Types

Choose an oral antihistamine in tablet, capsule, caplet or liquid form. A film of antihistamine dissolved on the tongue is good for a fast response. Medical personnel may choose to inject a solution or suspension of antihistamine or administer it in suppository form. Some nasal sprays include an antihistamine in the formula. Antihistamine eye drops combat symptoms in the eyes; antihistamine creams or gels provide relief on the skin.

Indications

An antihistamine can help when exposure to allergens causes symptoms such as swelling, runny nose, hives or itchy, watery eyes. "Medications such as oral antihistamines and inhaled antihistamines are first-line medications for mild to moderate symptoms of allergic rhinitis. These medications are best at targeting immediate symptoms such as a runny nose, itching, and sneezing as well as allergic conjunctivitis," reports Johns Hopkins Health Alerts. Antihistamines work alone or in combination with other drugs, such as decongestants, to tackle symptoms.

Time Frame

Use antihistamines at the onset of an allergic reaction to minimize the impact of symptoms. Take prescription antihistamines as directed by your physician to prevent histamine response, if you suffer from allergies on a regular basis.

Warning

Beware of drug interactions with antihistamines. Advise your doctor of all medications you take, including over-the-counter drugs and supplements. Check the information on the antihistamine label, including cautions about mixing with certain foods or other substances, such as grapefruit juice, alcohol or tobacco.

Side Effects

Potential side effects of antihistamines include dizziness or vertigo, sleepiness, irritability, feelings of faintness or dryness in the mouth or nose. Expect a higher occurrence in elderly patients. Seek a physician's advice when the patient is less than four years old, pregnant or suffering from a chronic condition requiring medication.

References

• Antihistamine; Mayo Clinic
• Allergy Medications: Know Your Options; Mayo Clinic
• Finding Relief from Allergies; Johns Hopkins Health Alerts