Which plants cause GI toxicity (stinging, inflammation, swelling of oral mucosa)?

• A. Nettle and Stinging Nettles
• B. Calcium-Oxalate Plants (Calla, Colocasia, Monstera, Philodendron)
• C. Mustards (Brassica)
• D. Castor Bean

Answer: (B)

Causing immediate irritation of the mouth when chewed is the hallmark here. Plants that contain calcium oxalate crystals have sharp needle‑like structures that physically irritate oral mucosa (a mechanical stinging), releasing irritants that trigger pain, burning, and swelling of the lips, tongue, and other oral tissues. This creates a rapid, local reaction in the mouth rather than a systemic toxin effect. Examples include Calla lily, Colocasia, Monstera, and Philodendron, which explains the described stinging and swelling of the oral mucosa.

In contrast, nettle stings are typically a skin phenomenon from contact, and castor bean and mustard group toxins tend to produce more generalized GI toxicity or systemic effects rather than the classic acute oral mucosal swelling after chewing. So the calcium-oxalate–containing plants best fit the presentation of GI toxicity with stinging and swelling of the oral mucosa.