Allergy Medications: Treatment with Decongestants, Antihistamines, Epinephrine

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For people suffering from allergies, a range of medications is available, both over the counter (OTC) and by prescription, to treat their illness. Pharmacological treatments exist for a wide range of allergy symptoms. They may be administered orally, or in the form of skin creams, eye drops, nasal sprays, or oral inhalers. Emergency allergy medications such as epinephrine may be administered through intramuscular injection.

Classes of Allergy Medications

Allergy medications can be divided into several classes depending on their pharmacology:

  • Epinephrine
  • Decongestants
  • Antihistamines
  • Corticosteroids
  • Leukotriene modulators
  • Mast cell stabilizers


Epinephrine, also called adrenaline, is used as a rescue medication in an allergic emergency (anaphylaxis). Patients at risk for anaphylaxis may carry portable epinephrine autoinjectors, which are available by prescription. These are designed to automatically inject a measured dose of epinephrine when activated and pressed against the body (generally the thigh muscle). Two brands are commonly available in the United States, the Epipen (the Epipen Jr. has a half dose for children) and the Twinject, which carries two doses in a single autoinjector. The reasoning behind the Twinject is that the symptom relief caused by epinephrine is short-lived and a second dose may be necessary before emergency medical help arrives.


Decongestants, such as pseudephedrine, merely treat nasal and sometimes eye congestion without addressing the cause of an allergic reaction. Oral decongestants are easily obtained OTC and are often combined with antihistamines. Nasal spray decongestants should be used for no more than two or three days in a row; otherwise discontinuation can cause even worse congestion called rebound congestion. Thus they are not suitable for long-term treatment of chronic allergic rhinitis.


Histamine is a chemical released by IgE-bound mast cells and basophils, the white blood cells behind allergic reactions, when an allergen triggers a reaction.  Histamine has several body roles, but most notoriously it causes inflammation.  Antihistamines are a class of drugs that block the inflammatory action of histamine, thereby preventing or reducing an inflammatory response.  Antihistamines are technically called H1 antagonists because they block histamine’s ability to bind to the H1 receptor, the one involved in inflammation; thus antihistamines do not affect histamine’s other roles in the body.

Antihistamine drugs include first-generation medications such as diphenhydramine (Benadryl), chlorpheniramine (Chlor-Trimeton), and others.  First-generation antihistamines can cause significant drowsiness; in fact, diphenhydramine is also used as a mild hypnotic.  Second-generation antihistamines such as loratadine (Claritin) and cetirizine (Zyrtec) are much less likely to cause drowsiness.

Antihistamines can be delivered in many different ways, including oral pills and tablets, topical creams, nasal sprays, and eyedrops.


This post is part of the series: Allergy Medications

Many allergy medications are available to provide allergy relief. Read about the different kinds of allergy treatments available to patients.

  1. Classes of Allergy Medications, Part 1