Peanut
One of the most common food allergies. Peanut is technically a legume, not a nut, although there is “cross-reactivity”, which means your risk of being allergic to tree nuts (eg cashew, hazelnut) is higher. Being allergic to peanut also means you are more at risk of allergy to other legumes (eg lentils, peas) and sesame.
So you can be allergic just to peanut, or lots of different nuts, and/or legumes, pulses, sesame, or some combination!
Peanut is also known as groundnut or monkey nut.
Tree nut allergy
The “official” list of tree nuts, at least as far as food labelling in the EU goes, is:
- Hazelnut
- Cashew
- Almond
- Brazil nut
- Pistachio
- Walnut
- Pecan
- Macadamia
You can be allergic to just one, or all, or something in between! And if you are allergic to one or more tree nuts, you have a higher chance of also being allergic to peanuts.
If you are allergic to cashew, you are usually also allergic to pistachio, and vice versa. If you are allergic to walnut, you are usually also allergic to pecan, and vice versa.
Testing
IgE blood test and Skin prick tests are available. Even if you are obviously allergic, testing is useful to look at other nuts/legumes that you may not eat routinely.
Component testing is a newer type of blood test, useful where you are trying to establish whether someone has the milder kind of peanut allergy seen in 
Oral Allergy Syndrome, although usually this is clear from the clinical history. Most people with peanut allergy are Ara h1 and/or 2 positive, which means they are potentially at risk of severe reactions. If you are only positive for Ara h8 then you are likely to have Oral Allergy Syndrome and the risk of severe reactions is much less. When it comes to just trying to prove allergy, regular (whole peanut) tests are better.
Family history
If you have one child with peanut allergy, the risk that a new baby will become allergic is only 5-9%. For this reason (and others) testing for people who have never had a reaction is not recommended – see Allergy tests
Avoidance
Avoiding peanuts can be difficult, as they are often used in biscuits, chocolate, breakfast cereal, muesli bars, ethnic foods eg satay etc.
Hazelnut is often found in chocolate eg Nutella chocolate spread (some chocolate spreads however do not contain nuts), praline, Kinder Bueno bars.
Cashew and almond are often used in Indian cooking, “Peshwari naan” often contains nuts. Cashew is often found in Chinese and South East Asian cooking eg Thai.
Cashew is often used in supermarket bought pesto (traditionally however, it is made with pine nuts – see below).
Pistachio is often used in ice cream (usually bright green colour is a clue) and in Indian sweets or desserts.
Italian cooking sometimes uses nuts eg Romesco sauce.
Salads and “health foods” eg muesli bars and protein bars often contain nuts.
The idea that a school can be “nut free” sounds good but in practice you can’t stop children (and teachers) bringing in snacks or treats containing peanut by mistake. Best to encourage good safe food habits in your child, in school and elsewhere!
If a food contains peanut or a tree nut, then it will be highlighted in bold in the ingredients list. Where something is labelled “may contain peanut/nut” or something similar, things get difficult. See Food Labelling for more on the issue of labelling.
See also Shopping, Eating Out, and Travel pages.
Peanut oil
Most industrially produced oils do not carry any allergy risk, as the proteins are removed during processing. By law, peanut oil has to be declared on labels – but probably very little risk of reacting to it. Unrefined peanut oil is different however, and is likely to provoke reactions.
Refined peanut oil is also found in some medicines eg vitamins so the same issues apply.
Avoid all nuts?
Some health care professionals advise that you avoid all nuts (peanut and tree nuts) even if you only allergic to one and there is no evidence that you are allergic to any other nut. This is because there might be accidental contamination, or because you or others might get confused. There is some evidence that you are less likely to have accidental reactions if you choose to avoid all nuts, but there is also evidence that quality of life increases if you do allow a child to eat nuts they are not allergic to (many peanut allergic kids really want to be eat hazelnut spread, for example). This should be a family decision.
Prognosis
Most children with peanut and/or tree nut allergy will remain allergic their whole life, only a minority outgrow it. Peanut immunotherapy is looking promising but is not yet widely available
Not Nuts
There are things which have “nut” in the name which are not related to peanut and tree nuts. It is possible to be allergic to them but this is rare, and being allergic to peanut or tree nuts does not increase the chance you are allergic to them:
- Coconut
- Pine nut
- Tiger nut
- Chestnut
- Water chestnut
See also Weaning and Antenatal, Curing Allergy