Yeast is a food additive which may result in allergy symptoms in sensitised individuals.

Yeast Allergy Test: Allergen Exposure

Yeast is a single-celled fungi that that multiplies by budding, or in some cases by division. It has been used by humans for millennia, commonly in the baking of bread and the preparation of beer, wine and other alcoholic beverages. The same species is used for both processes, but different strains and sub-strains have been adapted for and within both.

To gain energy from the breakdown of carbohydrates, the yeast ferments sugars, giving off carbon dioxide (CO2) and alcohol (ethanol). The CO2 is trapped as tiny bubbles in the dough, which consequently rises. In beer- and wine-making, the alcohol is the important product, although in beer and champagne the carbon dioxide may also be used.

In some markets, particularly Australia and the UK, specific human foodstuffs (Vegemite and Marmite) have been developed from brewer’s yeast.

The name Saccharomyces boullardii, for an organism now used in the treatment of intestinal disorders such as antibiotic-associated diarrhoea, is considered to be a synonym for a particular strain of Saccharomyces cerevisiae.

Yeast Allergy Test: Allergen Description

9 allergens present in yeast have been characterized, including a cyclophilin, a profilin, a glucosidase, and Sac c Enolase, a 46-51 kDa protein, an enzyme, and the most important allergen.

Yeast Allergy Test: Potential Cross-Reactivity

Allergenic cross-reactivity has been demonstrated between baker’s yeast, baker’s yeast enolase and Candida albicans. However, the cross-reactivity is complex.

In a study of sera of 54 patients with serum-specific IgE to C. albicans, IgE antibody to the C. albicans enolase was found in 20 sera (37%). Simultaneous IgE binding to S. cerevisiae enolase was observed in only 4 out of 20 sera reacting to C. albicans enolase. These results suggest that C. albicans enolase shares some cross-reacting epitopes with S. cerevisiae enolase, representing minor components of C. albicans enolase but dominant segments of S. cerevisiae enolase.

Yeast Allergy Test: Clinical Experience

Yeast may induce symptoms of allergy, including allergic rhinitis, asthma, and atopic dermatitis, in sensitised individuals. Hypersensitivity pneumonitis has been reported.

Yeast has been reported to be a significant cause of Bakers’ Asthma, a well-defined disease which can be caused by various antigens: flours and bran, yeast, baking additives, saprophytic moulds and storage mites.

Hypersensitivity to flour is a significant cause of Baker’s Asthma, but in recent years many more substances used in baked goods and pastry have been reported as causes of allergy, including yeast. Nevertheless, occupational asthma caused by this yeast is uncommon in bakers, despite the frequent use of this yeast. And although it is always present in the baking industry, it does not easily affect the airways and rarely sensitises workers.

Yeast is a major allergen, and has been reported to be a significant allergen in subjects who have respiratory allergy and show positive skin-specific IgE tests to Candida albicans and other fungi. This is not surprising, as the enolase allergen may function as a panallergen; other fungi will need to be considered in the evaluation of these patients.

Other reactions

Fungi cause a number of infectious diseases. These range from superficial skin lesions (primarily of cosmetic concern) to potentially fatal systemic mycoses.

Reports have indicated that yeast may result in allergic bronchopulmonary disease such as hypersensitivity pneumonitis.

A study reported over 2 decades ago that 33% of a group of patients with migraine were hypersensitive to yeast.