Eucalyptus for Cough Relief

Eucalyptus, a plant known for its aromatic properties, has been investigated in several clinical trials and randomized controlled trials (RCTs) for its potential efficacy in relieving cough. These studies aim to determine whether eucalyptus-based treatments, in various forms, can effectively alleviate cough symptoms and improve patient outcomes. The relevance of this research stems from the significant global burden of cough and the ongoing search for safe and effective non-pharmacological or complementary therapies.

Protocols Studied in Research

[1] Different honey types (eucalyptus, citrus, labiatae) and placebo (silan date extract) for nocturnal cough and sleep difficulty in children with upper respiratory tract infections (URIs). (Cited by: 37) (pmid: 22869830)

• Protocol: A double-blind, randomized, placebo-controlled study of 300 children (1-5 years old) with URIs and nocturnal cough. Participants received a single 10g dose of honey or placebo 30 minutes before bedtime. Outcomes were assessed via parental surveys.
• Outcome: All groups showed improvement, but honey groups demonstrated significantly greater improvement in cough frequency, severity, and sleep quality compared to the placebo group. Parents favored honey over placebo for symptom relief.

[2] Menthol inhalation for assessing its effect on nasal patency and cough in healthy children. (Cited by: 21) (pmid: 18435479)

• Protocol: A single-blind, crossover trial in 42 healthy 10-11 year olds compared menthol inhalation to eucalyptus oil (placebo). Nasal airflow, perceived nasal patency (VAS), and cough response to citric acid were measured.
• Outcome: Menthol did not improve objective nasal airflow measures but significantly increased the perceived nasal patency. The effect on cough reduction was not significantly different from placebo. Further research is needed in other populations.

[3] Menthol inhalation for citric acid-induced cough. (Cited by: 41) (pmid: 7974298)

• Protocol: Twenty healthy subjects received repeated citric acid inhalations as a cough challenge. Five minutes before each challenge, they randomly inhaled menthol (75% in eucalyptus oil) or placebo (pine oil or air).
• Outcome: Menthol inhalation significantly reduced cough compared to placebo, demonstrating its antitussive effect in this evoked cough model.

Research Interpretation: Summary and Conclusion

Three studies investigated the effects of eucalyptus (or components thereof, such as menthol) on cough, utilizing diverse methodologies. One study, using honey as a comparator, found significant improvements in cough frequency, severity, and sleep quality in children with upper respiratory infections (URIs) compared to placebo. However, two studies directly evaluating menthol in eucalyptus oil yielded mixed results. While one demonstrated a significant reduction in cough response to citric acid challenge in healthy adults, another found no significant cough reduction in healthy children compared to placebo, despite improving perceived nasal patency. Inconsistencies exist across studies regarding population (children vs. adults, healthy vs. ill), outcome measures (subjective vs. objective), and the specific form of eucalyptus used (menthol vs. whole oil). Further research, particularly well-designed, double-blinded RCTs employing consistent methodologies and focusing on specific eucalyptus components, is needed to clarify its efficacy in treating cough.

Publications

[1] Cohen HA; Rozen J; Kristal H; Laks Y; Berkovitch M; Uziel Y; Kozer E; Pomeranz A; Efrat H (2012). Effect of honey on nocturnal cough and sleep quality: a double-blind, randomized, placebo-controlled study Pediatrics 130 (3) :465-71.

[2] Kenia P; Houghton T; Beardsmore C (2008). Does inhaling menthol affect nasal patency or cough? Pediatric pulmonology 43 (6) :532-7.

[3] Morice AH; Marshall AE; Higgins KS; Grattan TJ (1994). Effect of inhaled menthol on citric acid induced cough in normal subjects Thorax 49 (10) :1024-6.