Q. Is the pencil cactus harmful to animals?
Pencil cactus is not actually a cactus. It is a member of a large family of succulent plants called Euphorbias. All members of this family produce a milky sap which is an irritant and a poison. It is not seriously harmful to dogs but if eaten it can irritate the mouth and stomach and may cause vomiting.
Contact with the plant can lead to skin rashes and blisters. The sap is also irritating to the eyes and may occasionally cause temporary blindness. However, pencil cacti are usually not a problem for dogs as they soon learn to avoid them Consult your local ASPCA about treatment if your dog becomes seriously affected, although this is rare.
Courtesy of NYBG Plant Information