A Guide To the RPAH Elimination Diet

by | Jun 14, 2022

Estimated to affect 10% of the population, pharmacological food intolerance involves a non-immunological reaction to natural compounds (e.g. salicylates, amines and glutamates) and/or artificial substances (e.g. preservatives, flavours and colours) found in food. People who are highly sensitive to one or more of these chemicals can experience unpleasant symptoms affecting various systems in the body (e.g. skin, airways, gastrointestinal, nervous system). Unlike food allergy which can often be diagnosed using a skin prick test or radioallergosorbent test, the only way to confirm a food intolerance/sensitivity is by undergoing an RPAH elimination diet.

What is the purpose of the RPAH elimination diet?

The RPAH elimination diet, followed by a chemical challenge, is used to diagnose patients whose symptoms are likely related to their diet.

Because natural and artificial chemicals are found in a wide variety of foods, and symptoms often present anywhere from 1 hour to 2 days after said foods have been consumed, it can be very difficult to pinpoint exactly what food/chemical is causing a reaction. Additionally, food intolerance/sensitivity is generally dose-dependent, meaning reactions only take place when an individual’s threshold is overshot, so it’s not generally a particular food item that causes a reaction, but an accumulation of the culprit chemical/s over time.

This is why linking diet to symptoms is not as simple as taking a test, but instead involves a very systematic approach in order to obtain a correct diagnosis.

What does the RPAH elimination diet involve?

Prior to undertaking the RPAH elimination diet it’s highly advisable to see a doctor to rule out any other health conditions as many of the symptoms of food intolerance/sensitivity overlap with other disorders.

If your GP can’t find other causes for your problems and you are experiencing symptoms that you suspect come about after eating certain foods, drinks or aspirin-containing drugs and/or have a history of skin rashes/itching, mouth ulcers, IBS, etc, you may be referred onto a dietitian for further investigation.

The elimination diet involves cutting out all possible trigger foods and their inherent provoking chemicals from the diet, leaving only a few foods that are unlikely to lead to a reaction. This restriction phase usually lasts for 4-6 weeks, giving you enough time to get through any withdrawal reactions which can occur in the first or second week, and then time to notice if your previous symptoms improve.

Often it will be recommended that you keep a food diary before you undergo an elimination diet. This is to give a clear picture of the severity and frequency of your symptoms – a reference for comparing how you feel during the elimination period.

It’s also worth mentioning that many of the chemicals people are sensitive to can be found in household products, perfumes, cosmetics, etc. so you will need to try and avoid these as much as possible in order to obtain an accurate picture of your sensitivity threshold. 

If there are no noticeable changes to symptoms during the 4-6 weeks on the strict elimination diet, then food intolerance/sensitivity is unlikely. If, however, during the elimination phase symptoms have cleared or have improved significantly for at least 5 days in a row, the challenge phase can take place.

What happens during the challenge phase?

When symptoms have cleared or improved significantly for 5 days in a row and an individual has been on the elimination diet for a minimum of 2 weeks then the challenge phase can begin.

This involves introducing foods containing only one challenge compound at a time, several times a day over several days to see if a reaction occurs (this can also be done using chemical capsules). Most often wheat and milk are challenged first followed by foods containing salicylates, amines, MSG, artificial colouring agents and finally a range of preservatives. On the first day, a small portion of the chemical is introduced. If no reaction occurs .you eat double the portion on the second day, and if no symptoms occur, on the third day you eat twice the amount as the second day. If a reaction does occur, this should be noted in a food diary. The person then needs to go back to their elimination diet until all symptoms have completely subsided after which 3 days need to pass before the next food challenge can begin.

Note that environmental and lifestyle factors can impact your chemical threshold so try to keep things as constant as possible during the challenge phase (easier said than done, I know). If something does occur left of field, make sure to note it in your food diary as a potential variable.

An example of the RPAH elimination/challenge process

What happens after completing the elimination and challenge phases?

When all the chemical challenges have been completed a dietitian will usually assess your reactions and recommend a modified diet, restricting chemical compounds that elicited a reaction. If there are any doubts about the results of one or more of the challenges, the whole process can be repeated. Due to the length of time it takes to conduct the elimination and challenge phases, it’s important that the process be strictly adhered to so as to avoid having to repeat.

After a month or two of eating on the modified diet, a gradual increase (by dose or frequency) of foods containing the symptom-inducing chemical can be carried out. This will allow you to observe where your chemical threshold lies. Remember that the elimination diet was never intended as a permanent way of eating. The ultimate goal is to liberalise your diet, eating as wide a variety of foods as possible without inducing symptoms.

Are there different approaches to the RPAH elimination diet?

Depending on the severity of your symptoms, their impact on your life and how restrictive with your diet you’re willing/able to be, there are three different approaches you can take with the elimination diet. A strict approach is for people who have debilitating symptoms that impact on their day-to-day and involves eliminating all foods except for those listed as “low chemical” which are unlikely to pose a problem. A moderate approach is for those whose symptoms are less severe and aren’t able to adhere to a highly restrictive diet in which case they will eliminate foods “high” and “very high” in their natural chemical content. Finally, for those with very mild and infrequent symptoms where relief can be felt from a few restrictions, cutting out only “very high” foods may be an option.

A discussion with your dietitian will help you to ascertain which approach is best for you. They will also provide you with information on the natural chemical content (e.g. low, medium, high) of a wide variety of foods.

What foods can you eat on the RPAH elimination diet?

Whilst certainly restrictive, the elimination does still allows for a variety of food to be consumed. The number of foods you can still eat is quite long so instead of listing them here, I suggest purchasing the RPAH food intolerance handbook which provides a very comprehensive overview of what you can and can’t eat along with the levels (low, medium, high) of salicylates, amines and glutamates found in each food. The book also includes a handy elimination diet shopping list and a meal planning guide.

For those not pursuing the strict elimination diet approach, you could also look at your family history for an idea of what to keep in your diet. For example, if your family has no history of reacting to wheat or lactose, it’s unlikely you will be sensitive to those foods either.

Of course, if your dietitian has already provided you with a list, it’s recommended to use that as it will have been constructed with your individual health needs/goals in mind.

Also, if you’re looking for some recipe inspiration using ingredients and foods allowed on the elimination diet, here are some suggestions:

Who is the RPAH elimination diet for?

The elimination diet is for people who are suffering from symptoms that are likely to be diet-related and when other health conditions have been ruled out by a doctor.

The elimination diet is not advised during pregnancy as the effects on the foetus have not been well studied. If you are pregnant and experience unpleasant symptoms you think could be associated with your diet, make sure to mention it to a healthcare professional.

An elimination diet may be suggested to the breastfeeding parent of a baby who develops symptoms such as hives or colic to see if any of the chemicals that are being transmitted through the milk may be causing the symptoms. It’s also recommended that an elimination diet while breastfeeding should only be undertaken if other strategies to identify causes of symptoms fail and always under medical supervision.

Elimination diets are not generally recommended for children due to the potential of developing nutritional deficiencies and/or food aversions. However, if an elimination diet is required, it’s imperative that it’s supervised by an accredited practicing dietitian.

People with asthma and other respiratory conditions should approach the challenge phase with caution, often in a hospital setting and always under the guidance of a healthcare professional.

Why is it important to see a dietitian when doing an elimination diet?

The elimination diet is restrictive and involves cutting out a wide range of food groups. In order to ensure adequate nutrition is maintained it’s recommended that you seek the guidance of a dietitian who can help you navigate the process. Uncovering food intolerances and sensitivities is serious business, and if done incorrectly can lead you to miss the real culprit and/or restrict foods unnecessarily; as if horrid symptoms themselves weren’t bad enough!

To search for a registered dietitian in Australia, you can use the search function on Dietitians Australia’s webpage.

What are some tips for doing the RPAH elimination diet?

Anyone who has been through an elimination diet will know how tedious it can be. Satisfying cravings is onerous, eating out is near impossible and the novelty of playing diet detective day-in day-out gets old fast. A challenging process to say the least, it’s important to remember that a crappy (relatively short-term) diet is infinitely better than a lifetime of crappy symptoms. So with that in mind, here are some tips for helping get through the frustrating yet enlightening journey that is the elimination diet – trust me, it’s all worth it in the end.

Brigid xx



1.) Gray PE, Mehr S, Katelaris CH, Wainstein BK, Star A, Campbell D, Joshi P, Wong M, Frankum B, Keat K, Dunne G, Dennison B, Kakakios A, Ziegler JB. Salicylate elimination diets in children: is food restriction supported by the evidence? Med J Aust. 2013 Jun 17;198(11):600-2. doi: 10.5694/mja12.11255. PMID: 23919705.

2.) Clarke, L., McQueen, J., Samild, A., & Swain, A. (1996). The dietary management of food allergy and food intolerance in children and adults. Australian Journal of Nutrition and Dietetics, 53(3), 89–97. https://www.slhd.nsw.gov.au/rpa/allergy/research/daareview.pdf

3.) Lozinsky AC, Meyer R, De Koker C, Dziubak R, Godwin H, Reeve K, Dominguez Ortega G, Shah N. Time to symptom improvement using elimination diets in non-IgE-mediated gastrointestinal food allergies. Pediatr Allergy Immunol. 2015 Aug;26(5):403-8. doi: 10.1111/pai.12404. PMID: 25963794.

DISCLAIMER: This article is for informational purposes only. It is not intended to constitute or be a substitute for professional medical advice, diagnosis, or treatment. 


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