Question 1. Is there an association between food allergy and asthma exacerbations?

From Chapter 8 of the Philippine Consensus Report on Asthma 2004 by the Philippine College of Chest Physicians.
This guideline starts below.

Is there an association between food allergy and asthma exacerbations?

Answer

Yes, the association between food allergy and asthma has now been clearly established.

Summary of Evidence

There is evidence that respiratory responses, including bronchoconstriction and increased airway hyperresponsiveness, have been demonstrated in individuals following positive food challenges. However, food-induced asthma in adults is actually not very common, with an incidence of only 2-8.5%. The clinical correlation of food allergy with asthma is much higher in children at 17%.

Multiple food allergy is generally uncommon. In infants and children, the majority of allergic reactions are due to milk, eggs, soy, peanuts and wheat, while in adults, the most common food allergens are peanuts, tree nuts, fish, shellfish, and eggs.

Sulfite-containing foods have been shown to cause bronchospasm and severe asthmatic attacks in sensitive asthmatic patients, although the mechanism by which sulfate agents worsen asthma is unknown. The relationship between monosodium glutamate (MSG) and asthma is more controversial with several groups reporting both association and non-association. The mechanism by which MSG produces asthma attacks is not well understood. There is conflicting evidence as to whether MSG exacerbates or induces asthma or if it alters airway reactivity. Tartrazine (FD&C Yellow No. 5) and other dyes commonly used for artificial coloring of food, drink, pills and tablets have been reported to cause urticaria and asthmatic symptoms in a few sensitive patients.

Asthma exacerbated by food allergy should be suspected in the following circumstances:

• If asthma started early in life, especially if associated with atopic dermatitis.
• If asthma associated with a current or part history of food allergies or atopic dermatitis.
• If wheezing after specific foods has been noted.
• If asthma poorly controlled even with appropriate medications and aeroallergen avoidance.

Food-induced asthma may present acutely, occurring within minutes to one hour of food ingestion, manifesting initially with itchy watery eyes and nose, and itchiness in the mouth. This may later on progress to deep, repetitive coughing, shortness of breath, and wheezing. Acute attacks of asthma may be severe and occasionally progress to systemic anaphylaxis and even death. Respiratory reactions from food allergens may also be subtle, at times presenting only with cough, chronic asthma, or increased BHR.

The diagnosis of food allergy is dependent on adequate history and physical examination, skin testing or in vitro antigen-specific IgE tests, results of an appropriated exclusion diet and blinded provocation when this may be performed safely.

Food-induced asthma is confirmed if food challenge reveals wheezing, a significant drop in FEV1, or a positive methacholine challenge on the test day but not on the placebo day. Elimination of the suspected food is often tried as part of a diagnostic approach. If symptoms resolve, confirmation by food challenge is recommended, except in cases wherein the patient has a convincing history of systemic anaphylaxis to a specific food.

Following identification of allergenic food, strict elimination of that food is the only treatment proven effective to prevent reactions. The use of oral desensitization, prophylactic medications, or immunotherapy has not yet been demonstrated in well-designed studies to have clear efficacy in the management of food allergies.