Diagnosis of Food Allergy - Physical examination

The focus of the physical examination varies, depending upon the patient’s presenting symptoms, their acuity, chronicity, and the mechanism suspected, based upon the history. In those patients presenting in the midst of an acute allergic reaction to a food.

Attention is directed to the upper and lower airway to determine whether significant airway obstruction caused by laryngeal edema or bronchospasm is present or evolving, as severe laryngeal edema and bronchospasm refractory to treatment are common causes of death in food-induced anaphylaxis.

Continuous monitoring of the oxygen saturation during these reactions is required. Other airway findings, such as marked nasal congestion, repetitive sneezing, profuse clear rhinorrhea, hoarseness, stridor, coughing, accessory muscle use, nasal flaring, and wheezing should be noted.

Close monitoring of the vital signs and physical examination for changes suggestive of impending shock, such as delayed capillary refill or changes in mental status, is indicated, as refractory shock is the other major cause of death in these reactions.

Cutaneous changes, including flushing, generalized pruritus, angioedema, urticaria, and flaring of eczema are often encountered, along with gastrointestinal findings of oropharyngeal edema, increased or decreased bowel sounds, abdominal tenderness, vomiting, or diarrhea.

Physical findings, such as allergic shiners, conjunctival injection, clear rhinorrhea, nasal congestion with a pale, edematous nasal mucosa, a transverse nasal crease, wheezing, and xerosis or patches of eczema observed in a less acute setting, suggest the presence of other allergic disease and increase the likelihood of coexistent IgE-mediated sensitivity to foods.

Occasionally, an associated physical finding may suggest a specific diagnosis or raise concern about more serious disease. For example, the presence of a rash consistent with dermatitis herpetiformis suggests a diagnosis of celiac disease.

The diagnosis of dermatitis herpetiformis should be considered in the patient with ‘‘eczema’’ not responding to standard therapy, as mistaking dermatitis herpetiformis for eczema has been reported. Careful monitoring of weight and growth parameters at each visit and over time is required for food allergic patients.

Weight loss, or failure to thrive, is rarely encountered in patients with IgE-mediated reactions to few foods or those less pervasive in the diet.

Alternatively, patients with nonIgE-mediated or mixed gastrointestinal allergy, young children with food refusal, or patients on severely restricted diets because of suspected or documented multiple food allergy may fail to maintain their weight.

Although specific or multiple food refusal in young children with limited verbal ability is often attributed to behavioral issues, further questioning and a careful physical examination is indicated to rule out other potential causes.

Infants and toddlers often shun foods to which they are allergic, as the ingestion of these foods causes oropharyngeal tingling and burning, a metallic taste, abdominal pain, or nausea. Children with active esophagitis or dysphagia may avoid solid foods swallowed as a firm bolus, because the resultant esophageal distention or spasm is painful.

Other potential causes of food refusal in these children include chronic or intermittent aspiration resulting from swallowing disorders, or oral tactile defensiveness in which certain food textures are not tolerated. Continued weight loss, or failure to thrive and not responding to dietary intervention to provide adequate caloric intake, should prompt further evaluation to rule out other disease.