Peanut allergy

See also Prevention, pregnancy, EAT/LEAP studies and immunotherapy.

One of the most common food allergies.  Peanut is technically a legume, not a nut, although there is cross-reactivity.  Always consider if there are potentially other allergies to lentils, sesame, tree nuts eg cashew etc.

Also known as groundnut or monkey nut.

[Gary Stiefel, Leicester Royal, BSACI guideline peanut allergy]

Diagnosis

Wide range of potential peanut proteins.  In US study, vast majority were Ara h1/2 positive, but European more diverse. h1, h2, h3 most common for systemic reactions.  Testing with whole peanut is always going to be most sensitive.

peanut allergy diagnosis BSACI 2017With a decent history, SPT >3mm or IgE >0.35 sufficient.

Distinguish Pollen Food Syndrome – ie older, rhinitis, oral allergy symptoms with nuts/fruit. These kids will have a milder allergy.  Hazelnut mostly (Cor a1) but almond, peanut, walnut too. But can coexist with more severe allergy! Doing grass/birch pollen would support diagnosis, doing components might help assess prognosis. If history unclear, but positive IgE/Skin prick test then do components h2 and h8 (list of different cut offs for different commercial products given, with related specificity/sensitivity but just says positive/negative in flow chart!).

Sibling risk 5-9%. Too low to justify routinely screening.  Do SPT to encourage home challenge!?

Prognosis

Up to 20% will outgrow. Review may not be necessary if PFS only.  Follow up is essentially about education.  Testing can be done periodically, depending on resources.

Avoidance

Difficult, as often used in biscuits, chocolate, ethnic foods eg satay.

Precautionary labels – impossible to eliminate risk. Snack foods higher risk incl biscuits, cakes [Helen Brough]. Stratify risk according to previous reactions, threshold, asthma. Crossing the road metaphor!

Should you avoid all nuts?  Some kids will be allergic to other (tree) nuts, but not all.  Andrew Clark reports v low rate of accidental reactions, 3%, with avoidance of all nuts. But increases quality of life to be allowed other nuts!  Risk assessment.

Peanut oil

Probability of any reaction to refined peanut oil is remote (Blom et al, 2017). Little evidence that anyone has ever reacted to refined peanut oil. Code of practice is that presence of UNREFINED peanut oil should be declared on bottles of oil (UK and Europe).

But peanut oil, even if refined, still has to be declared on food labels.  Beware unrefined oil in ethnic foods.  Also found in some medicines eg vitamins.

Some suspicion that peanut oil in cosmetics and pharmaceuticals might lead to sensitization and subsequent peanut allergy, even if not enough peanut protein to cause a reaction in an allergic person. So advice is avoid if you have a strong family history of allergy.

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