What is the recommended treatment for allergic reactions using antihistamines?

From the Guidelines

Antihistamines are the first-line treatment for mild to moderate allergic reactions, with second-generation (non-sedating) antihistamines like cetirizine, loratadine, or fexofenadine being recommended due to their lower risk of sedation and anticholinergic effects compared to first-generation options. For acute allergic symptoms, these non-sedating antihistamines are preferred as they cause less drowsiness and have a faster onset of action, typically within 30 minutes to 1 hour, with peak plasma concentrations reached within 1-3 hours 1.

Key Considerations for Antihistamine Use

• Second-generation antihistamines such as cetirizine (10mg daily), loratadine (10mg daily), or fexofenadine (180mg daily) are recommended for their efficacy and lower side effect profile compared to first-generation antihistamines 1.
• First-generation antihistamines like diphenhydramine (Benadryl) at 25-50mg every 4-6 hours may be more effective for severe itching or hives but cause sedation, making them less ideal for daytime use or for patients who need to maintain alertness 1.
• Treatment duration should be tailored to the individual's response, typically continuing until symptoms resolve, which can be 3-7 days for acute reactions or throughout the allergy season for seasonal allergies 1.
• Chronic allergies are best managed with daily non-sedating antihistamines to control symptoms effectively without the sedative side effects associated with first-generation antihistamines 1.

Severe Allergic Reactions

For severe allergic reactions involving breathing difficulty or significant swelling, antihistamines alone are insufficient, and emergency medical attention is necessary as epinephrine (via an EpiPen) may be required 1. Epinephrine is the first-line treatment for anaphylaxis due to its rapid onset of action and ability to address the life-threatening aspects of the reaction, such as hypotension and bronchospasm 1.

Additional Considerations

• Glucocorticoids may be used as adjunctive therapy in the treatment of anaphylaxis but should not be administered prior to or in place of epinephrine, given their slow onset of action and lack of proven benefit in preventing biphasic anaphylaxis 1.
• Biphasic anaphylaxis prevention does not have strong evidence supporting the use of antihistamines or glucocorticoids, with recommendations against their use for this purpose due to low certainty of evidence and potential for delaying first-line epinephrine treatment 1.

In summary, antihistamines are a crucial component of managing allergic reactions, with second-generation options being preferred for their safety and efficacy profile. However, for severe reactions, epinephrine remains the cornerstone of treatment, with antihistamines and glucocorticoids playing adjunctive roles.

From the FDA Drug Label

PRINCIPAL DISPLAY PANEL-500'S COUNT Rising® 16571-402-50 Original Prescription Strength Cetirizine Hydrochloride Tablets USP 10 mg 6 yrs & older Antihistamine ALLERGY Indoor & Outdoor Allergies 24 Hour Relief of: •Sneezing •Runny Nose •Itchy, Watery Eyes •Itchy Throat or Nose 500 Tablets T10 - M.L. G/1430

The recommended treatment for allergic reactions using antihistamines, such as cetirizine, is to provide 24 Hour Relief of symptoms including:

• Sneezing
• Runny Nose
• Itchy, Watery Eyes
• Itchy Throat or Nose 2 Important warning: Do not use if you have ever had an allergic reaction to this product or any of its ingredients or to an antihistamine containing hydroxyzine 2.

From the Research

Antihistamines for Allergic Reactions

• Antihistamines are commonly used to treat allergic reactions, with first-generation antihistamines like diphenhydramine having adverse effects on the central nervous system 3.
• Newer antihistamines, such as loratadine, desloratadine, cetirizine, and fexofenadine, are considered safer options with less sedation and similar efficacy 3, 4, 5.
• Loratadine is a nonsedating antihistamine with once-daily dosing, reaching peak plasma concentration in 1-2 hours and having a duration of action of at least 24 hours 4.
• Cetirizine has the fastest onset of action among newer antihistamines, while fexofenadine does not impair psychomotor or cognitive skills and shows no dose-related increase in sedation 3.

Recommended Treatment

• The recommended treatment for allergic reactions using antihistamines is to use newer, second-generation antihistamines, which provide similar efficacy to first-generation antihistamines but with less sedation 3, 5, 6.
• A nonsedating, nonimpairing second-generation antihistamine is preferred for all patients, particularly those with a higher risk for the development of adverse effects 5.
• Ebastine is a once-daily, non-sedating, selective, long-acting second-generation antihistamine that appears to be safe, effective, and well-tolerated in the treatment of allergic rhinitis and chronic idiopathic urticaria 7.

Key Considerations

• The choice of antihistamine should be based on factors such as sedative potential, effect on cognitive function, efficacy, onset of clinical activity, and cost 3, 6.
• Conditions that result in accumulation of certain antihistamines, such as astemizole, ebastine, and terfenadine, may prolong the QT interval and result in torsade de pointes 6.
• Antihistamines can be used to treat various allergic disorders, including allergic rhinitis, urticaria, and atopic dermatitis 6, 7.