Signs and Symptoms of Food Allergy

Anaphylaxis

Anaphylaxis is a potentially life-threatening clinical syndrome characterized by the sudden onset of generalized symptoms, affecting multiple organ systems in the body.

Symptoms typically occur less than 2 hours, often minutes after ingestion of food. Rarely, food-related exercise-induced anaphylaxis may occur where the susceptible individuals experience the reaction after exercising within 2 to 4 hours of food ingestion but not with food or exercise alone.

Skin and other organ system manifestations

1. Skin

Skin lesions are the most common manifestations of IgE mediated food hypersensitivity. Signs range from acute urticaria (itch) and angioedema (swelling of the skin) to an rash. Chronic urticaria is almost never caused by food allergy.

2. Gastrointestinal

Gastrointestinal complaints are the second most frequent manifestations. The main clinical features are vomiting, diarrhoea and abdominal pain. Although patients with functional bowel disease (e.g. non-ulcer dyspepsia and irritable bowel syndrome) may often describe certain foods aggravating their symptoms, there have not been any controlled studies demonstrating any immunological role of food in these disorders.

3. Respiratory

Airway symptoms like sneezing, rhinorrhea (runny nose), wheeze and dyspnoea (shortness of breath) when present in isolation without other organ complaints (e.g. persistent allegic rhinitis or asthma) are rarely due to food allergy.

When due to food allergy, these airway symptoms are usually present as part of a generalized anaphylactic reaction. Only 6-8% of children with moderate to severe asthma may have food associated wheeze. In contrast, 1% of adult asthma is associated with food, often in the form of occupational asthma among workers from the food industry.

Pollen-food allergy syndrome (Oral allergy syndrome)

This is a form of contact allergy to food allergens, usually a fresh fruit or vegetable. The involved food is only an allergen source when it is fresh as the proteins involved are heat labile.

Symptoms include pruritus (itch) with possible angioedema (swelling) of the lips, tongue, palate and posterior oropharynx. Only rarely may other organs be involved.

Oral allergy syndrome is associated with specific pollen allergy in individuals with seasonal allergic rhinitis as cross-reactive proteins e.g. profilins are found in both the fruit/ vegetable and common pollens. This is uncommon locally as the predominant cause of allergic rhinitis is house dust mite allergy.

Other reactions

Allergic inflammation of the esophagus and gastroenteritis may also occur in some instances. Symptoms include postprandial nausea and vomiting, abdominal pain and diarrhoea, GI reflux, premature feeling of fullness or refusal to eat, weight loss in adults and growth failure in children.

These symptoms usually subside within 3 to 6 weeks after the allergen is eliminated although gut activity may not return to normal for months.

Inflammation in the digestive system

Food-induced inflammation of the intestines affects infants between 1 week and 3 months old. The main symptoms are vomiting and diarrhoea which frequently results in dehydration.

The infant may appear ill and septic. Food-induced inflammation of the rectum and colon may also occur but symptoms are milder and involvement is limited to the colon and rectum.

The typical picture is that of a well appearing infant with blood-streaked or bloody stools. In both conditions, symptoms usually resolve after 72 hours of allergen avoidance. Cow’s milk and soy protein are the most frequent culprits. Infants usually outgrow this allergy. Similar but less severe reactions have been reported in adults.

Such inflammation often occurs in the first few months of life. Doctors may diagnose this disorder by detecting diarrhea, bloatedness of the tummy, flatulence, and failure to thrive. Cow’s milk is the most frequent cause although soy, egg, wheat, rice, chicken and fish have been implicated. Patients tend to outgrow their food allergy.

Celiac disease produces more serious reactions due to the sensitivity to gluten. Symptoms are similar to that of malabsorption. Lifelong avoidance of gluten containing food is necessary to control symptoms and avoid the increased risk of malignancy. This is uncommon locally.