| Drug | Effect |
| Alfalfa | Irritant, canavanine in seeds |
| Arnica | Irritant to mucous membranes |
| Asafoetida | Irritant gum |
| Blue flag | Irritant gum and oil |
| Bogbean | Irritant to GI tract |
| Boldo | Irritant oil |
| Buchu | Irritant oil |
| Capsicum | Capsaicinoids, mucosal irritants |
| Cassia | Irritant to mucous membranes, oil |
| Cinnamon | Irritant to mucous membranes, oil |
| Cohosh, blue | Irritant to mucous membranes; spasmogenic in vitro |
| Cowslip | Irritant saponins |
| Drosera | Plubagin, irritant |
| Eucalyptus | Irritant oil |
| False unicorn | Large doses may cause vomiting |
| Figwort | Purgative effect |
| Garlic | Raw clove |
| Ground ivy | Irritant oil |
| Guaiacum | Avoid if inflammatory condition |
| Horse-chestnut | Saponin constituents, contraindicated in existing renal disease |
| Horseradish | Irritant oil |
| Hydrangea | May cause gastroenteritis, hydrangin |
| Jamaica dogwood | Irritant to humans |
| Juniper | Irritant oil |
| Lemon verbena | Irritant oil |
| Lime flower | Irritant to kidney, oil |
| Nettle | Tea irritant to stomach |
| Parsley | Irritant oil |
| Pennyroyal | Toxic and irritant oil |
| Pilewort | Irritant sap |
| Pleurisy root | Gastrointestinal irritant |
| Pokeroot | Irritant saponins |
| Pulsatilla | Irritant to mucous membranes |
| Queen's delight | Diterpene constituents |
| Sarsaparilla | Saponins |
| Senega | Saponins |
| Skunk cabbage | Inflammatory and blistering to skin |
| Squill | Saponins |
