|
This Month連 Feature Review:
The Prognosis of Severe Food Allergy
Vincent St Aubyn Crump - Auckland Allergy Clinic
The prevalence of food allergy is estimated to be as high as 6% in young children and approximately 2 % in adults. The highest prevalence occurs between 1.5 and 3 years of age.
All the Allergy literature states that about 80% of children with milk and egg allergy will outgrow their allergy by the age of five but only about 20% of peanut-allergic kids will outgrow their allergy. But the prognosis of food allergy is not that black and white. In reality there are several shades of grey, like:
" Children with milk and egg allergy, who also have peanut allergy, are less likely to outgrow their milk and egg allergy than those without peanut allergy.
" Adults can develop severe food allergies, which usually persist.
" Food allergies can be temporarily outgrown in children. There has been a recent report from Hugh Sampson et al at Mt Sinai School of Medicine of 3 children who outgrew their peanut allergy based on reduced CAP-RAST and negative oral challenges, who re-sensitized and developed clinical symptoms after re-introducing peanuts back into their diets. There are also 2 case reports from Spain of re-sensitization to fish after a short time of tolerance.
Food allergy tends to be a problem of early childhood and is often replaced by respiratory allergy, which appears in middle to later childhood as food allergy wanes, i.e., the atopic march.
Click here for full Article
Intolerance of cow連 milk and Chronic Constipation in children
Guiseppe Iacono, MD., et al, Divisione di Pediatria, Universitia di Palermo, Palermo, Italy
Background: Chronic diarrhoea is the most common gastrointestinal symptom of intolerance of cow連 milk among children. On the basis of a prior open study, we hypothesized that intolerance of cow連 milk can cause severe perianal lesions with pain on defecation and consequent constipation in young children.
Methods: we performed a double blind, cross-over study comparing cow連 milk with soy milk in 65 children (age range, 11 ?• 72 months) with chronic constipation (defined as having one bowel movement every 3 to 15 days). All had been referred to a Paediatric gastroenterology clinic and had previously been treated with laxatives without success; 49 had anal fissures and perianal erythema or oedema. After 15 days of observation, the patients received cow連 milk or soymilk for 2 weeks. After a one-week washout period, the feedings were reversed. A response was defined as eight or more bowel movements during a treatment period.
Results: 44 of the 65 children (68%) had a response while receiving soymilk. Anal fissures and pain with defecation resolved. None of the children who received cow連 milk had a response. In all 44 children with a response, the response was confirmed with a double-blind challenge with cow連 milk. Children with a response had a higher frequency of coexistent rhinitis, dermatitis, or bronchospasm than those with no response (11 of 44 children vs. 1 of 21. p=0.05); they were also more likely to have anal fissures and erythema or oedema at base line (40 of 44 vs. 9 of 21. p<0.001), evidence of inflammation of the rectal mucosa on biopsy (26 of 44 vs. 5 of 21, p=0.008), and signs of hypersensitivity, such as specific IgE antibodies to cow連 milk antigens (31 of 44 vs. 4 of 21, p<0.001).
Conclusions: In young children, chronic constipation can be a manifestation of cow連 milk intolerance.
Reference: NEJM Volume 339:1100-1104, October 15, 1998
Pets, parental atopy, and asthma in adults
Jouni J.K. Jaakkola, MD, DSc, PhD et al, Goteborg, Sweden, and Helsinki, Finland
Background: Studies of exposure to pets and the risk of asthma have provided conflicting results.
Objective: We conducted a population-based incident case-control study to assess the relationship of current and previous pet keeping with the risk of adult-onset asthma. We also investigated whether genetic propensity as a result of parental atopy modifies these relations.
Methods: From the source population of 441,000 inhabitants of a geographically defined area of South Finland, we systematically recruited, during a 2.5-year period, all new cases of asthma in 21- to 63-year-old adults and randomly selected control subjects. The clinically diagnosed case series consisted of 521 adults with newly diagnosed asthma and a control series of 932 control subjects. Information on current and past exposure to hairy pets was collected by using a self-administered questionnaire.
Results: In logistic regression analysis the risk of asthma was lower among subjects with pets during the last 12 months (adjusted odds ratio [OR], 0.74; 955 confidence interval [CI], 0.57-0.96) but higher among subjects with pets more than 12 monthS previously (adjusted OR, 1.39; 95% CI, 1.05-1.84). Parental atopy increased the risk of asthma (OR, 1.88; 95% 1.47-2.41), but there was no interaction between parental atopy and pet exposure.
Conclusions: The present results were consistent with the hypothesis that both keeping furry pets and parental atopy increase the risk of asthma development in adulthood. Parental atopy does not modify the effects of pet exposure. The negative association between current pets and risk of asthma is consistent with selective avoidance of these pets by symptomatic individuals.
Reference: J Allergy Clin Immunol 2002; 109: 784-8
Prevention of sensitisation to house dust mite by allergen avoidance in school age children: a randomised controlled study
S. H. Arshad, et al and SPACE (Study of the Prevention of Allergy in Children in Europe) Study group.
Background: Sensitisation to dust mites predisposes to asthma and allergic rhinitis, and the prevention of this sensitisation might reduce the rising prevalence of these disorders.
Objective: To test the effectiveness of the dust avoidance measures on the development of sensitisation to dust mite in children.
Methods: As part of a multicenter study (Study of the Prevention of Allergy in Children in Europe), 242 children, aged 5-7 years, in three European countries (UK, Greece and Lithuania), were randomised to prophylactic group (n=127) and control group (n=115). At randomisation these children were required to have a family history of atopy and positive skin prick test to an aeroallergen but not to house dust mite. Children in the prophylactic group were provided with dust mite impermeable mattress covers and advice on environmental measures to reduce exposure to dust mites allergen. Control group children were given non-specific advice. After 12 months a standardized questionnaire was completed and skin prick tests performed.
Results: 10 children in the prophylactic group and 19 in the control group were lost to follow-up. 3 of the 117 (2.56%) children in the prophylactic group and 9 of 96 (9.38%) in the control group developed sensitisation to dust mites. Logistic regression analysis confirmed an independent effect of prophylactic measures (adjusted odds ratio (OR): 0.14, 95% confidence interval (CI): 0.03-0.79, p=0.03). 15 children needed to be treated to prevent sensitisation in 1 child.
Conclusions: Dust mite sensitisation can be reduced in school age children with simple mite avoidance measures.
Reference: Clinical & Experimental Allergy, Vol 32, Issue 6, Page 843 ?• June 2002-06-05
A double-blind, placebo-controlled study on the diagnostic accuracy of an electrodermal test (VEGA test) in allergic subjects
M. Semizzi et al, Allergy Service, Verona Major Hospital, Verona, Italy
Background: many unconventional diagnostic procedures based on bioelectrical skin responses are presently widely used for allergic diseases, but rigorous experimental evaluations of their accuracy are still lacking.
Aim: We assessed whether an electrodermal device can correctly diagnose respiratory allergy.
Methods: The diagnostic accuracy of the electrodermal device was assessed in double-blind fashion in 72 allergic patients and 28 healthy volunteers. A random sequence of substances in sealed vials, including histamine, allergens, immunoglobulins at various dilutions and physiological saline, were tested in duplicate in each subject.
Results: A wide variability of the measurements was found in most patients irrespective of their allergy status and of the substances tested. Allergic patients showed more negative skin electrical response at the second trial, compared to normal controls, independent of the tested substance. No significant difference in skin electrical response between allergens and negative controls could be detected.
Conclusions: We conclude that the studied bioelectrical method, under blind testing, cannot correctly detect respiratory allergy.
Reference: Clinical & Experimental Allergy, Vol 32, Issue 6, Page 928 ?• June 2002
|
