A mucous membrane irritant will produce a heating or drying effect on the mucous membranes of the mouth, eyes, nose, and reproductive organs. It is recommended that mucus membrane irritating essential oils not be used in a full body bath unless placed in a dispersant first (e.g., milk, vegetable oil). It would also be wise to put the dispersed essential oils into the water after you have gotten into the bath. Bay, clove, cinnamon bark, lemongrass, and thyme ct. thymol essential oils should be avoided in baths completely. The Table lists some common essential oils considered to be mucous membrane irritants.
Mucous membrane irritants :
| Essential Oil | Latin Name |
| Bay | Pimento racemosa |
| Caraway | Carum carvi |
| Cinnamon bark or leaf | Cinnamomum zeylanicum |
| Clove bud or leaf | Syzygium aromaticum |
| Lemongrass | Cymbopogon citratus |
| Peppermint | Mentha x piperita |
| Thyme ct. thymol | Thymus vulgaris |