Route Of Exposure

Allergen Exposure

Gum arabic has been used for at least 4,000 years. The substance is a gummy exudate derived from trees of the species Acacia senegal and its close relatives. The trees are found in Sudan, Senegal, Nigeria and other semi-arid regions. The dried exudate is odourless, colourless and tasteless, and often occurs in response to infection. To stimulate production of this exudate, wounds are intentionally made. A distinguishing characteristic among natural gums is that Gum arabic dissolves rapidly in water.

Gum arabic is a thickener, emulsifier, and stabiliser, and a glazing and flavouring agent. It is often used to retard sugar crystallisation. It is considered a valuable food in parts of Asia and Africa.

It is a complex polysaccharide, primarily indigestible to both humans and animals, not degraded in the intestine, but fermented in the colon under the influence of microorganisms. Apple fiber and Gum arabic reportedly lower total and low-density lipoprotein cholesterol levels in men with mild hypercholesterolemia.

Unexpected exposure

Gum arabic is a demulcent in cosmetics and medicines. It is often an ingredient in toiletries. It is an anti-offset agent in printing, and is also important in lithography, in the manufacture of inks and adhesives, in the textile industry and in the production of galactose.

Combretum gums, readily available at low prices, may be offered for sale as “Gum arabic”. Vigilance is necessary to detect such misrepresentations, because Combretum gums differ greatly from Gum arabic.

Clinical Relevance

Allergen Description

In a study, Gum arabic-specific IgE antibodies of a patient were directed mainly against the carbohydrate fraction of the material; due to the repetitive polysaccharide sequence of Gum arabic, several epitopes for the cross-linking of IgE should exist.

Potential Cross Reactivity

An extensive cross-reactivity among the different individual species of the genus could be expected but in fact is not seen frequently. In an in vitro study, the specific IgE binding by protein extracts of 11 food legumes was examined by RAST and RAST inhibition. Cross-allergenicity was demonstrated to be most marked among the extracts of Peanut, Garden pea, Chick pea, and Soybean.

However, clinical studies have found that there is little cross-reactivity among members of the Fabaceae (Leguminosae).

Cross-reactivity between Gum arabic and Tragacanth gum has been reported.

Clinical Experience

IgE-mediated reactions

Gum arabic may uncommonly induce symptoms of asthma, allergic rhinitis, eczema, contact dermatitis and food allergy in sensitised individuals.

A study reports on a male who experienced 4 allergic incidents after drinking coffee. Dual sensitisation to coffee and to the Gum arabic coating of roasted coffee beans was demonstrated by skin-specific IgE and by human basophil degranulation tests. Two serious anaphylactic reactions with cardiac arrest occurred, which were attributed to concomitant treatment with beta-blocking eye drops (Timolol). Beta-blocking drugs produce a loss of compensatory cardiovascular mechanisms and make those who take them resistant to the conventional treatment for anaphylactic shocks, which explains the serious accidents that occurred in this patient.

Occupations where workers may be exposed to Gum arabic include cosmetics, ceramics, fireworks, carpet and other textile manufacturing, the food and pharmaceutical industries, hairdressing, printing, and mining.

Allergic rhinitis, asthma and eczema caused by Gum arabic in workers in a candy factory have been reported.

Occupational allergy from mist inhalation in printers has been reported and is called “Printer's Asthma”. Allergy reactions have also been reported in patients working in the pottery and lithography industries and occupational asthma in printers and carpet manufacturers

Other Reaction

Chronic alveolitis due to repeated and prolonged inhalation of sweets containing Gum arabic is reported in a study.