Determining eliciting doses in walnut allergic patients

Most patients with food allergy adhere strictly to their diet to avoid the
relevant food. Therefore, most reactions take place by hidden allergens or
suboptimal labeling of food products. Good labeling is essential in preventing
food allergic reactions. The current legislation is inadequate.
A first step in improving laws and regulations is to
quantify the effects of certain concentrations of allergens in products. This
requires knowledge of eliciting doses. The eliciting dose is defined as the
lowest amount of allergen that is required to elicit an allergic reaction and
is derived from double-blind placebo-controlled food challenges which are also
used in routine daily practice to diagnose a food allergy.
At this moment, eliciting doses for some well-known food
products that can trigger an allergic reaction (peanut, hazelnut, milk, egg)
have been established by food challenges in representative populations. For
walnut these data are still lacking while it is the third most common food
allergy in the Netherlands and the fourt most common in Europe.

Establishing an eliciting dose distribution for walnut on population level by
determining individual eliciting doses in double-blind placebo controlled food
challenges.

Visit 1: characterization of patients by skin prick test and blood tests
Visit 2 and 3: food challenge
Visit 4 (only in case of a positive food challenge and after particular
informed consent for this extra visit): blood withdrawal

Food challenge with walnut food for all participants

First visit: 1 hour and 2 provocation days of each 8 hours, possible 4th visit
of 30 minutes. The skin prick test is a safe test and is routinely performed in
the outpatient department clinic. In most cases, the participant will get a
wheal (looks like a mosquito bite). The itching disappears after 15-30 minutes
and the wheal itself after about 2-3 hours. The risk of the blood collection
and intravenous drip during food challenge is a slight pain and the possibility
of a bruise.
The result of a food challenge is an allergic reaction that can range from mild
symptoms (itching in the mouth) to a (rarely) anaphylactic reaction. During
provocation, there are good precautions to minimalize the risk: medications can
be administered immediately by the intravenous drip if needed and there will be
a continuous observation until 2 hours after provocation by experienced nurses
who work daily with food challenges. The whole food challenge is performed
under the supervision of a physician.