How are allergies treated?
Antihistamines are used to treat allergic reactions. These drugs work by blocking the action of histamine, a substance that is produced by the body in response to an allergen and that causes the allergic reaction. Antihistamines are particularly useful in the treatment of hay fever symptoms. They are also given to relieve itching and irritation of the skin (such as hives) and for mild acute allergic reactions. They are of no benefit in asthma. Sedating antihistamines include chlorpheniramine (Chlor-trimeton), cyproheptadine, hydroxyzine (Vistaril), diphenhydramine (Benadryl), and promethazine. These may cause drowsiness as a side effect, which can be useful in some conditions such as itchiness of the skin at night. Nonsedating antihistamines are also available. These include cetirizine (Zyrtec), desloratadine (Clarinex), fexofenadine (Allegra), levocetirizine (Xyzal), and loratadine (Claritin). Antihistamines are available as tablets and/or liquid. Some antihistamines can be purchased from a pharmacist without a prescription.

For allergic reactions causing nasal symptoms such as sneezing or runny nose, an anti-inflammatory drug such as cromolyn nasal spray may be effective. Other antihistamines are also available as nasal sprays, for example, azelastine. Corticosteroid nasal sprays may also be given. These may contain beclomethasone (Beconase AQ), budesonide (Rhinocort Aqua), flunisolide, fluticasone (Flonase, Veramyst), mometasone (Nasonex) or triamcinolone (Nasacort AQ). Decongestants such as pseudoephedrine (Sudafed) can be useful for short-term treatment of sinusitis or prior to flying.

Combination products containing an antihistamine and a decongestant are also available. For hay fever affecting the eyes, there are several antihistamine eye drop preparations available including azelastine (Optivar), ketotifen (Alaway, Claritin Eye, Zaditor, Zyrtec Itchy Eye Drops), olopatadine (Pataday, Patanol), and emedastine (Emadine). Antihistamine and vasoconstrictor combination eye drops (eg, pheniramine and naphazoline [Naphcon A]) are also available to treat allergy symptoms and redness.

In asthma, specific treatment is prescribed and includes the use of inhalers and other medication.  More information on asthma can be found at www.cdc.gov/asthma.

Anaphylactic reactions require immediate treatment, usually with a combination of antihistamines and epinephrine given in an injection form. People who have a known allergy that can result in anaphylaxis (such as those with bee-sting or peanut allergies) should carry the drug with them at all times (in the form of a prefilled injector—Auvi-Q,EpiPen). The prescribing doctor can provide a letter describing the allergy and the medical necessity of having the injector available at all times, including on an airplane.

Further Information
National Institutes of Health: http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001815/

Last Reviewed: May 2013