Antihistamines are commonly used medications that help manage various allergy symptoms. While effective at reducing issues like sneezing and runny nose, their ability to dry up mucus depends on the specific type.
The Role of Mucus and Histamine
Mucus is a protective substance lining bodily surfaces, particularly in the respiratory system. It traps and removes harmful particles like dust, allergens, bacteria, and viruses. Mucus also moistens and lubricates membranes. During allergic reactions or illnesses, the body can increase mucus production as a defense mechanism, leading to symptoms like a runny nose.
Histamine is a chemical released by the immune system in response to allergens or irritants. It plays a role in the body’s inflammatory and allergic reactions. When histamine binds to receptors, it can cause symptoms such as itching, swelling, and increased mucus production, contributing to a runny nose.
How Antihistamines Reduce Mucus
Antihistamines primarily work by blocking histamine at H1 receptors. By preventing histamine from binding, they reduce symptoms triggered by an allergic reaction, including excessive mucus production, itching, and swelling.
Some antihistamines also have anticholinergic properties, blocking acetylcholine. Acetylcholine stimulates glands that produce secretions, including those in mucous membranes. When these properties are present, they reduce secretions, leading to the drying of mucous membranes and a decrease in mucus and saliva production.
Different Antihistamines, Different Effects
Antihistamines are categorized into two main generations, with varying effects on mucus drying. First-generation antihistamines, such as diphenhydramine (Benadryl) and chlorpheniramine (Chlor-Trimeton), cross the blood-brain barrier, contributing to their sedative properties.
These first-generation medications have pronounced anticholinergic effects. This action causes significant drying of mucous membranes, reducing secretions like mucus and saliva. They are more likely to dry out nasal linings and thicken mucus.
Second-generation antihistamines, including loratadine (Claritin), cetirizine (Zyrtec), and fexofenadine (Allegra), are more selective for peripheral H1 receptors and minimally cross the blood-brain barrier. This results in less sedation and fewer anticholinergic effects. Consequently, second-generation antihistamines generally do not cause significant mucus drying.
What to Know About Mucus Drying
The mucus-drying effect of certain antihistamines can offer relief from a runny nose. However, this drying action can also lead to dry mouth or dry nasal passages.
While antihistamines can reduce mucus production, they may also make existing mucus thicker and more difficult to clear. This can be noticeable with first-generation antihistamines, potentially exacerbating postnasal drip. Maintaining good hydration by drinking plenty of fluids is recommended to help thin mucus. If symptoms persist or worsen, or if adverse effects like excessive dryness become problematic, consult a healthcare professional.