What proportion of people with IgE sensitisation to flour have symptoms due to allergy?

It has been widely reported that the majority of individuals in bakeries who have nasal or respiratory symptoms do not have any evidence of IgE sensitisation. In addition my own observation is that individuals with positive IgE often have either no or minimal symptoms (in a similar way to individuals who are IgE positive for grass pollen not always having symptoms of hayfever). Even where symptoms are present, they can be difficult to link with exposure to allergen, suggesting that the sensitisation may be incidental rather than causal. Is there any any evidence to demonstrate what proportion of bakery workers experience symptoms as a direct result of their IgE sensitisation?

Occupational Asthma, Specialist, 8/21/2007, 8/22/2007,

Some of these questions are easy, some more difficult Most agree that there are bakery workers with work-related rhinitis or asthma without specific IgE to flour or amylase. Whether the mechanism is not IgE mediated, or due to an allergen not measured, is not certain, but both are probably true (for instance flour antigens differ betwen different grains and other enzymes may be used, and at least in the past azodicarbonamide was sometimes in bread (where no IgE I believe has been found) I think all would agree that sensitisation (having specific IgE) is found in a greater proportion than have any disease. This would certainly be true of common allergens such as grass pollen. I think incidental sensitisation is not a usual term. To get sensitised exposure must occur first. The exposure might however be to a cross-reacting allergen, for instance between wheat and grass. There are several studies which only consider occupational asthma or rhinitis in bakers who have specific IgE and ignore those with occupational asthma without specific IgE, whether the groups differ in important outcomes is not known to me. The attached reference considers all non IgE work-related symptoms as irritant. I believe that you cannot say a reaction is irritant solely because of the absence of identifyable IgE, for the reasons above. It would be important to follow-up those thought to be irritant and those thought to be allergic to see if their outcomes differ Smith TA, Lumley KP, Work-related asthma in a population exposed to grain, flour and other ingredient dusts, Occup Med, 1996;46:37-40,

8/22/2007