I found this on a Carp website.
Peanuts
This particle has been banned on many waters. This was due to bad publicity following many carp deaths some years back when a batch of bacteria infected nuts were introduced to waters in vast quantities. They are also lacking in some proteins and vitamins, and if carp begin to feed to exclusively on them, they will suffer health problems. However, if used sensibly, they can make a very good carp bait. Make sure that you only purchase the human grade type as the ones intended for bird tables may be of a poorer quality and contain a toxic fungus. The safest way to decide is to think "would I eat these" If the answer is no, then why should the carp. This is actually a rule I apply to a lot of my baits, including boilies. Chocolate malt are my favourite, but watch out for the scopex dipped ones!
Peanuts must be prepared by soaking for 24 hours and then boiling for 15 - 20 minutes. You can add flavours as above if you wish.
Why the Nut that is Not a Nut Can Be Dangerous
For starters, the peanut (arachis hypogea) is actually not a nut at all. It is a bean -- and a peculiar one at that. It is part of the legume family, and while most of the beans found in this family grow in pods on sprawling, climbing vines, the peanut plant is a lonely bush that matures its pods underneath the ground in a root system.
It is primarily due to the peanuts' direct contact with the soil that they have become harmful, and even dangerous, to your health.
While actual nuts like almonds and walnuts have strong, hard shells that protect them, the legume known as a peanut has soft and porous skin. When the environment surrounding the peanut becomes warm, humid and wet -- as it does in most regions of the U.S. where peanuts are commonly grown -- a fungal growth occurs.
The fungus itself is not dangerous, but the poison it releases, known as "aflatoxin," is. This cancer-causing agent attacks the liver and is one of the more deadly food-borne toxins in existence.
Largely because of the regions they're commonly grown in and the fact that they're relatively easy for pests to attack and penetrate, peanuts are also one of the crops most heavily sprayed with pesticides. So the standard peanut packs a double-whammy risk to your health.
But don't mourn another convenient, tasty and otherwise nutritious food icon being shot to pieces -- there are healthy solutions for young and old peanut-lovers alike...
It sounds to me that it is more the quantity of the grade of nut that you introduce rather than 1 non grade human peanut on a hair rig that is the concern.
If you use Human Grade Peanuts, and they're just not catching the fish you can always eat them instead.
