The sap of a bougainvillea is mildly toxic, but the leaves are not. The thorns of a bougainvillea can prick the skin and cause dermatitis.
Ingesting enough of the bougainvillea sap can cause illness. Other hazards of the plant include prickly thorns sharp enough to tear through fabric. Because of the danger of scratches and cuts, this plant should not be used in play areas or near swimming pools. The plant can also cause allergic reactions that include itching, redness, swelling, blisters, rash, stinging, burning and skin sores. These plants are generally found in USDA hardiness zones 9 through 11. A Brazilian native, the bougainvillea is a perennial featuring showy flowers and bright leaves.