Are antihistamines (anti-allergic medications) effective for treating asthma?

From the Guidelines

Antihistamines are not recommended as a primary treatment for asthma, as they do not address the underlying inflammatory mechanisms of the disease. While antihistamines like cetirizine, loratadine, and diphenhydramine work well for allergic conditions such as hay fever by blocking histamine receptors, they don't address the primary mechanisms of asthma, which involves airway inflammation and bronchoconstriction through different pathways 1. The standard medications for asthma include inhaled corticosteroids (like fluticasone or budesonide) to reduce inflammation, bronchodilators (like albuterol or salmeterol) to open airways, and leukotriene modifiers (like montelukast) that target specific inflammatory pathways involved in asthma 1.

Some key points to consider when evaluating the effectiveness of antihistamines for asthma include:

• Antihistamines may reduce peak seasonal wheezing associated with severe rhinitis symptoms, but they are not recommended for the treatment of asthma 1
• In patients with allergic rhinitis and concomitant asthma, cetirizine and desloratadine may relieve upper and lower respiratory tract symptoms, but they do not alter pulmonary function 1
• Antihistamines like levocetirizine may decrease symptoms and improve quality of life in patients with persistent allergic rhinitis and asthma, but they are not a substitute for standard asthma medications 1

In general, antihistamines might help reduce exposure-related symptoms in patients with allergic asthma triggered by specific allergens, but they won't treat the underlying asthma condition itself 1. This is because asthma involves multiple inflammatory mediators beyond just histamine, including leukotrienes, prostaglandins, and cytokines that aren't affected by antihistamine medications. Anyone with asthma should work with their healthcare provider to develop an appropriate treatment plan using asthma-specific medications rather than relying on antihistamines.

From the FDA Drug Label

PURPOSE Antihistamine USE(S) temporarily relieves these symptoms due to hay fever or other upper respiratory allergies:  runny nose  sneezing  itchy, water eyes  itching of the nose or throat

The provided drug labels do not mention asthma as a condition that can be treated with antihistamines. The labels only discuss relief from symptoms of hay fever or upper respiratory allergies.

• Key points:
  • Antihistamines are used for allergic reactions.
  • The labels do not explicitly state that antihistamines are effective for asthma. Therefore, based on the information provided in the drug labels 2 and 2, antihistamines are not indicated for asthma treatment.

From the Research

Effectiveness of Antihistamines for Asthma

• Antihistamines have been evaluated as potential therapies for asthma for more than 50 years, with second-generation compounds showing promise due to reduced side effects 3.
• Studies have found that certain antihistamines, such as terfenadine, cetirizine, and loratadine, can improve asthma symptoms and pulmonary function in mild and moderate allergic asthma 3.
• However, the effectiveness of antihistamines for severe perennial asthma is limited, and higher doses may be required to achieve significant benefits 3, 4.
• The combination of antihistamines with other medications, such as decongestants or leukotriene-receptor antagonists, may enhance their effects and improve asthma symptoms 3, 5.

Clinical Evidence and Studies

• A study published in 2003 found that cetirizine improved asthma symptoms compared to placebo or terfenadine in patients with mild and moderate allergic asthma 3.
• Another study published in 2006 found that antihistamines, such as azelastine, cetirizine, desloratadine, and fexofenadine, had beneficial effects on asthma symptoms or physiological measures in patients with asthma 5.
• However, a study published in 1979 found that inhaled clemastine was not a clinically useful bronchodilator either acutely or as a maintenance treatment for asthma 6.

Mechanisms and Potential Benefits

• Antihistamines block the actions of histamine and have effects on inflammation independent of histamine-H(1)-receptor antagonism, which may contribute to their potential benefits in asthma management 5, 4.
• Antihistamines have been shown to have bronchodilatory effects, prevent allergen-induced nonspecific airways hyperresponsiveness, and delay or prevent the development of asthma in atopic children 5, 4.