From the Guidelines
Antihistamines can thicken mucus by reducing the amount of water in the mucus, making it more viscous and harder to clear. According to the study by 1, antihistamines may act to reduce coughing by the suppression of mucus production in upper respiratory infections (URI). However, they do not break down existing mucus or make it thinner.
Some key points to consider:
- Antihistamines work by preventing histamine from binding to H1 receptors, thereby reducing mucus production 1.
- First-generation antihistamines like diphenhydramine (Benadryl) and chlorpheniramine (Chlor-Trimeton) have anticholinergic effects, which can dry out the nasal mucosa and thicken mucus 1.
- Second-generation antihistamines like cetirizine (Zyrtec), loratadine (Claritin), and fexofenadine (Allegra) have less anticholinergic effects and are less likely to thicken mucus 1.
- Expectorants like guaifenesin (Mucinex) are more effective at thinning mucus by increasing the water content, making it less viscous and easier to clear 1.
It's essential to note that antihistamines are most helpful for allergy symptoms, including runny nose, sneezing, and itchy eyes, while decongestants address congestion, and expectorants handle thick mucus. For best results with antihistamines, take them regularly during allergy season rather than only when symptoms appear, as they work better preventatively 1.
From the Research
Antihistamines and Mucus Thickness
- The effect of antihistamines on mucus thickness is not directly addressed in the provided studies 2, 3, 4, 5, 6.
- However, some studies suggest that antihistamines may affect mucus production and secretion in the respiratory tract.
- For example, a study found that loratadine, a non-sedating antihistamine, reduced the allergen-induced release of histamine into the nasal cavity and decreased the TAME-esterase activity, which is involved in mucus production 4.
- Another study found that antihistamines have a marked inhibiting effect on hypersecretion in the nose, suggesting that they may reduce mucus production 6.
- However, it is not clear whether antihistamines thicken or thin mucus, as the studies do not provide direct evidence on this topic.
- Some studies suggest that antihistamines may have a drying effect on secretions in the upper and lower respiratory tracts, but this is not universally accepted and may not be relevant to mucus thickness 3.