Borage

What borage does to a cat.

Borage is toxic to cats. The ASPCA lists it as toxic, with the clinical signs: "Vomiting, diarrhea, dermatitis." It is usually a mild-to-moderate upset rather than a life-threatening poisoning — but between the irritant bristles and the alkaloids in its seeds, borage is firmly a herb for people, not for cats.

Borage (Borago officinalis) is a bristly, blue-flowered annual in the family Boraginaceae, grown as a culinary herb (its leaves taste faintly of cucumber) and as a bee plant. The pressed seed oil is sold as "starflower oil."

ASPCA Data

According to the ASPCA, borage is listed under plants toxic to cats, with the signs:

Vomiting, diarrhea, dermatitis.

There are three distinct ways this plant troubles a cat, and they are worth separating.

Why borage is toxic

1. Contact dermatitis from the bristly leaves

Borage leaves and stems are densely covered in stiff bristly hairs. Simple contact — brushing against the plant or mouthing a leaf — can irritate a cat's skin and mouth, which is the "dermatitis" the ASPCA notes. This happens before any toxin is even absorbed.

2. Gastrointestinal upset

Eaten, borage causes vomiting and diarrhea. For most cats this is self-limiting and settles once the plant is out of the system, but it is unpleasant and can lead to dehydration if it drags on.

3. Pyrrolizidine alkaloids in the seeds and oil

The more serious concern is chemical. Borage seeds and the pressed borage (starflower) oil contain pyrrolizidine alkaloids (PAs) — compounds that are hepatotoxic, meaning they can damage the liver with significant or repeated exposure. The leaves contain much less, but this is the reason borage oil supplements should never be given to a cat and should be stored out of reach.

What to do if your cat eats borage

A single curious nibble usually means a bit of drooling or a bout of stomach upset rather than a crisis. Still, do not wait it out blindly:

1. Remove any remaining plant and rinse the mouth if your cat will allow it.
2. Watch for vomiting, diarrhea, skin redness, and lethargy.
3. Call your vet or ASPCA Animal Poison Control at (888) 426-4435 if a large amount was eaten, if the seeds or borage oil were involved, or if symptoms persist or worsen.

Safe herb alternatives

If you grew borage for the kitchen or for the bees, several ASPCA non-toxic herbs give you the same cottage-garden harvest without the toxicity: basil, dill, and thyme are all safe around cats.

The bottom line

Borage is toxic to cats — irritant bristles, vomiting and diarrhea, and hepatotoxic alkaloids in its seeds and oil. It is rarely fatal, but it has no place within a cat's reach. Grow a safe herb instead, and keep any starflower-oil supplements firmly out of paw's way.