Exhaled nitric oxide decreases after positive food-allergen challenge.

BACKGROUND: Exhaled nitric oxide (FeNO) is a well described marker of airway inflammation in asthma and is also known to increase after chronic exposure to inhaled allergens. It is not known whether monitoring FeNO could be useful during food challenges to detect early or subclinical reactions. METHODS: Forty children aged 3 to 16 years undergoing an allergen-food challenge at two centres were prospectively recruited for this study. FeNO was assessed before and repeatedly after the food-challenge. RESULTS: Data were obtained from a total of 53 challenges (16 positive, 37 negative) and were compared between the two groups. Half of the patients with a positive food challenge exhibited clinical upper respiratory symptoms. The FeNO significantly decreased in 7 of 16 patients with a positive challenge test within 60 to 90 minutes after the first symptoms of an allergic reaction. CONCLUSION: Our results show a significant decrease in FeNO after a positive food challenge suggesting involvement of the lower airways despite absence of clinical and functional changes of lower airways. Prospective blinded studies are needed to confirm these results.

An overview of cow's milk allergy in children.

Food allergies have increased over the past decade and are an important problem in daily clinical practice. They affect 6% of children and 3 to 4% of adults. Furthermore, around 20% of the population falsely believe that they are allergic to some foods and follow unnecessarily restrictive diets. For infants, the problem is even more acute as they need appropriate feeding in order to achieve normal growth and avoid bone and metabolic problems. Although any food can cause a reaction, few foods are responsible for the large majority of the symptoms: i.e., milk, eggs, wheat, peanuts, nuts, fish, shellfish. Of these, cow's milk allergy is frequently suspected in small children. It can be responsible of a variety of symptoms and can be caused by IgE-mediated or non-IgE-mediated reactions. The diagnosis relies on a detailed history, skin tests, laboratory tests, an elimination diet and food challenges. The overall natural evolution of the disease is favourable with most patients achieving tolerance to milk by the age of five years, but some patients will remain allergic for life.

Correlation between specific immunoglobulin E levels and the severity of reactions in egg allergic patients.

Different studies proposed specific immunoglobulin E (IgE) cut-off levels for the diagnosis of egg allergy. Little is known if IgE titres could be helpful for prediction of the severity of the reaction. The aim of this study was to determine whether IgE titres are associated with the severity of the reaction during a standardized egg challenge. We reviewed data obtained during oral challenge tests to egg performed between 2003 and 2005, and attributed a clinical score to the positive reactions. Serum specific IgE levels were analysed in relation with the severity of the reaction. We analysed data from 51 oral food challenges to egg, raw or cooked. Sixteen challenges (31%) were negative and 35 (69%) were positive of which 13 challenges (37% of positive reactions) elicited a severe reaction. IgE levels in our patients ranged from undetectable to 14.90 kU/l. We could determine a cut-off level of 8.20 kU/l for a 90% probability of clinical reactivity. IgE titres were statistically significantly different between the patients with absent, mild and moderate or severe reaction. Patients with negative challenge had IgE levels between 0.35 and 6.41 kU/l (median 1.17), those with mild and moderate reaction had IgE levels ranging from 0.35 to 14.90 (median 2.47) and patients with severe reactions had IgE between 1.18 and 11.00 (median 3.70) (p = 0.006). Our results show a correlation between IgE titres and the severity of the clinical reaction to egg. IgE titres may help to determine the potential risk of a reaction to eggs.