The Reading-based firm claims to be the first lab in the UK to offer a commercial testing service that can include pistachio, pecan, celery and mustard.
Tougher European rules on allergen labelling, due diligence duties, and the threat of potentially brand-destroying product recalls have all combined today to raise the use of out-sourced allergen testing by food manufacturers.
"Since we launched our original allergen test two years ago, we have seen a significant increase in demand," says Barbara Hirst, technical manager of the molecular biology department at RSSL.
Hirst and her team are behind the latest expansion of allergen commercial tests that can now detect pistachios, pecans, celery and mustard.
The test uses polymerase chain reaction (PCR) techniques to amplify and detect specific morsels of DNA that relate to particular allergens.
"The test is extremely sensitive to each allergen, but we do have a stated detection limit," Hirst tells FoodNavigator.com.
According to the scientist, the most common demand today for the test, that costs between £100 to £200 a sample, is when emergencies arise.
A customer eats a product that provokes a reaction, so the food maker forwards the sample onto RSSL for testing. With a potential product recall overhanging the sample, the test - that can take up to two days - can be turned around in under 12 hours, says RSSL.
Due diligence, "customers send us samples on a regular basis to check that their product is nut free when it declares it is", is also growing, motivated crucially by new European rules on allergen labels.
Introduced in November 2004, and due for total enforcement by 25 November this year, EU Directive (2003/89/EC) requires food makers to provide a comprehensive ingredients listing on the label of potential food allergens; essentially to flag up to the consumer any potentially harmful ingredient.
The amendment, that also marks an end to the 20 year old '25 per cent rule', heralds the mandatory inclusion on food labels of the most common food allergen ingredients and their derivatives: cereals containing gluten, fish, crustaceans, egg, peanut, soy, milk and dairy products including lactose, nuts, celery, mustard, sesame seed, and sulphites.
The introduction of tougher labelling rule was largely driven by the steep rise in allergy sufferers.
An estimated 4 per cent of adults and 8 per cent of children in the EU - the total population tops 380 million - suffer from food allergies, according to the European Federation of Allergy and Airways Diseases Patients' Associations.
There is no current cure for a food allergy, and vigilance by an allergic individual is the only way to prevent a reaction: but a peanut allergy can be so severe that only very tiny amounts can be enough to trigger a response.