Table 2.

Overview of the immunomodulatory effects and concentrations of selected essential oils.

Essential Oil	Effects on Immune Functions	Concentrations
Eucalyptus	Increased the phagocytic activities of macrophages and peripheral blood monocytes and enhanced bacterial clearance [34,36]; restored the number of circulating granulocytes and their phagocytic ability in immunosuppressed models [34]; inhibited the production of IL-1α, IL-1β, IL-4, IL-6, TNFα, and NO [34,36]; attenuated the activation of p38 MAPK, NFκB, and TREM-1 [36]; suppressed COX-2 promoter activity by 25% [1]	EEO 0.008 and 0.016% [v/v] (in vitro), EEO 12 mg/kg/day for 15 days (in vivo) [34]; EEO and 1,8-cineole 0.02% [v/v] (in vitro) [36]; EEO 0.01% (in vitro) [1]
Clove	Many contradictory results; stimulated cell-mediated immunity in immunocompetent mice and restored WBC count and humoral immunity in immunosuppressed mice [54]; inhibited cell-mediated responses and improved humoral immune responses in immunocompetent rats [55]; suppressed NO and TNFα production by macrophages [58]; stimulated [58] and inhibited [62] IL-6 production; enhanced cell-mediated and humoral immune responses in experimental VL [56]; suppressed COX-2 promoter activity by 40% [1]	CEO (<98% eugenol) 100, 200, 400 mg/kg/day for 7 days (in vivo) [54]; CEO (87.34% eugenol) 0.1 mL/kg/day (in vivo) [55]; ethanolic CEO extract (74% eugenol), aqueous CEO extract (43% eugenol) 0.001–1000 µg/mL (in vitro) [58]; clove extract 100 µg/well, eugenol extract 50 and 100 µg/well (in vitro) [62]; eugenol emulsion 25, 50, and 75 mg/kg/day for 10 days (in vivo) [56]; CEO 0.01% (in vitro) [1]
Tea tree	Stimulated the differentiation of immature myelocytes into active phagocytizing monocytes and increased CD11b receptor expression [68]; suppressed the production of TNFα, IL-1β, IL-8, IL-10, and prostaglandin E2 by blood peripheral monocytes [2]; MAC reduced the production of NO and proinflammatory cytokines, inhibited NFκB activation and induced HO-1 expression [65,67]	TTO and terpinen-4-ol 20-90 µmol/L (in vitro) [68]; water soluble components of TTO at 0.125% (42% terpinen-4-ol, 3% α-terpineol and 2% 1,8-cineole) (in vitro) [2]; MAC (60–64% terpinen-4-ol, 8–14% p-cymene) 0.004–0.016% [v/v] (in vitro) [65]; MAC (60% terpinen-4-ol) 0.01–0.5% (in vitro) [67]
Lavender	Increased the phagocytic activity of macrophages and reduced intracellular bacterial replication and the production of IL-1α, IL-1β, and IL-6 [73]; attenuated IL-5 and IL-13 secretion and inhibited eosinophilic infiltration and mucus production in mouse asthma models [77]; aromatherapy massage increased IgA levels [74] and the number of CD8+ and CD16+ cells [75]	LEO (39% linalool, 11.97% camphor, 10.54% eucalyptol) dilution of 1:50,000 for 106 cells (in vitro) [73]; LEO (31.78% linalyl acetate, 25.56% linalool) 20 µL on 10 × 10 filter paper (in vivo) [77]; LEO 2% (aromatherapy clinical trial) [74]; essential oil blend of lavender (36.31% linalool, 34.05% linalyl acetate), cypress (61.85% β-pinene, 15.2% 3-carene), and sweet marjoram (21.26% terpinen-4-ol, 13.46% γ-terpinene) (aromatherapy clinical trial) [75]