"The poisons cause rashes similar to seaweed dermatitis upon skin contact with various fauna, such as Loafpicks and their relatives." That doesn't say it's limited to them.
You could simply say lyngbyatoxin A and debromoaplysiatoxin, the toxins it uses, don't work on it because its biochemistry is so different from Loafpicks, and until recently (evolutionarily speaking) Loafpicks were its biggest trampling concern.