The sword fern—also commonly known as the Boston fern or fishbone fern—is generally characterized as a nontoxic plant that is safe to have around children and pets. Still, the sword fern, like any other plant, can cause an unexpected allergic reaction in some individuals.
Allergens vs. Toxins
Sword ferns are nontoxic, which means they do not contain poisons which cause illness. Toxins are poisons—natural or man-made—that do damage in proportion to the dose that is ingested or inhaled. Allergens are irritants that can cause an adverse reaction—regardless of dosage—in individuals whose immune system has previously encountered and misidentified the substance as a toxin.
While sword ferns are harmless to most people and pets even if ingested, some people who come into prolonged contact with wet fronds of the fern may develop certain irritations.
According to scientists at the University of Oklahoma, symptoms of an allergic reaction to sword or Boston fern might include red itchy skin, small fluid-filled blisters known as vesicles, scaling of the skin and swelling around fingernails and toenails.
The symptoms of contact dermatitis from other plants such as poison ivy are similar, and it is rarely possible to pinpoint the cause of your allergic reaction unless your contact was limited to only one kind of plant.
If you notice symptoms of contact dermatitis from sword ferns or other plants, experts at the University of Virginia Health System suggest thoroughly washing the area with soap and water as soon after exposure as possible. To soothe irritated skin, they suggest using wet, cold compresses. For severe reactions, you should contact your physician.