Food-Allergy Fears Drive Overly Restrictive Diets, Study Suggests

ScienceDaily (Nov. 4, 2010) — Many children, especially those with eczema, are unnecessarily avoiding foods based on incomplete information about potential food-allergies, according to researchers at National Jewish Health. The food avoidance poses a nutritional risk for these children, and is often based primarily on data from blood tests known as serum immunoassays.

Many factors, including patient and family history, physical examination, and blood and skin tests, should be used when evaluating potential food allergies. The oral food challenge, in which patients consume the suspected allergenic food, is the gold standard test.

The researchers conducted a retrospective chart review of 125 children evaluated at National Jewish Health for suspected food allergies. Depending on the reason for food avoidance, 84 percent to 93 percent of foods being avoided were restored to their diets after an oral food challenge. The researchers published their study online in The Journal of Pediatrics on Oct. 29. It will appear in a later print version of the journal. "People with known food allergies, especially those with a history of anaphylactic reactions, should by all means avoid those foods," said David Fleischer, MD, lead author of the study and Assistant Professor of Pediatrics at National Jewish Health. "However, a growing number of patients referred to our practice are being placed on strict, unproven food-elimination diets that have led to poor weight gain and malnutrition. These overly restrictive diets have been chosen for a variety of reasons, but overreliance on immunoassay tests appears to be the most common cause."

Immunoassays detect antibodies in the blood to specific foods, which can potentially cause allergic reactions. Interpretation of the results, however, can be tricky. The tests' ability to predict true food allergy has been validated for only five foods -- cow's milk, hen egg, fish, peanut and tree nuts.

For all other foods, the numbers derived from lab testing are suggestive but not definitive. Low test values suggest that a child's immune system is sensitized to the food, but not necessarily to the extent that it will cause an allergic reaction. Higher values suggest an increasingly likelihood of true food allergy. None of the tests are 100 percent accurate, however, in predicting clinical food allergy on their own.

National Jewish Health physicians use blood tests as one piece of evidence in their comprehensive evaluation of food allergy. They also carefully evaluate a patient's history, including any previous reactions to food, the type of reaction, the patient's age, and the result of skin testing for food allergy. They generally perform an oral food challenge when the evidence is mixed and they want a definitive answer to the food allergy question.

Children in the study were avoiding 177 different foods based primarily on previous blood test results. In many cases, especially those with high test results for egg, milk, shellfish, peanut and tree nut, National Jewish Health elected not to perform oral food challenges. They did perform oral food challenges for 71 foods or about 40 percent of the cases where the clinical allergy was equivocal and it was important to determine whether or not the patient had food allergy. In 86 percent of those cases, the child passed the food challenge and the food was restored to the child's diet. Overall, 66 of the 177 foods avoided because of blood tests were restored to children's diets. For the entire study, 325 foods were restored to the diets of 125 children.

"When you are able to restore foods such as dairy products, egg, peanut, wheat, and vegetables to a child's diet, it improves their nutrition, reduces the need for expensive substitute foods and makes meal time easier for families," said Donald Leung, MD, PhD, senior author and Edelstein Chair of Pediatric Allergy and Clinical Immunology at National Jewish Health.

The problem can be especially acute among patients with eczema, also known as atopic dermatitis. Research suggests that specific foods can cause flare-ups in about one third of eczema patients. They commonly have high immunoassay tests to a variety of foods, many of which are not truly allergenic. As a result, many mistakenly avoid foods they believe are causing flare-ups, but neglect basic skin care that is vital to improving the eczema. One hundred and twenty of the 125 children in the study had eczema.

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Fighting Wrinkles With Lasers Scientifically Unraveled

ScienceDaily (Oct. 25, 2010) — Laser pulses enable skin rejuvenation, as research at Eindhoven University of Technology (TU/e) has shown. Laser treatment introduces heat into the skin. Under the influence of heat shocks of 45°C, skin cells produce more collagen. This is the protein that gives the skin its firmness and elasticity. Susanne Dams describes this process in the dissertation for which she gained her PhD degree from the Biomedical Engineering Department at TU/e.

Laser treatment is quite common in the practices of beauticians and dermatologists. Although the technique has been widely used for many years, its impact and the underlying processes are still to be unraveled. The effect of light has been studied before, but according to researcher Susanne Dams there is still little understanding about the effect of the heat introduced by a laser. Research performed by Dams now provides a better understanding of this process.

The researcher first tested the effect of heat on cell cultures, by giving them heat shocks of 45 and 60°C without a laser. This excluded possible effects generated by the laser light. Subsequently, she conducted similar tests on pieces of excised human skin, and at a later stage she heated pieces of skin with a laser. The results of these tests were in line with the earlier tests.

She showed that the heat shocks led to increased production of collagen, which is considered to be one of the important factors in skin rejuvenation. The production of this protein by the human body declines after the age of 25, causing wrinkles to form and making the skin sag. The best effect was found to result from a heat shock of 45°C lasting eight to ten seconds. It was also shown that higher temperatures cause damage to the skin cells. Dams established in her tests that heating cells in culture for two seconds at 60°C results in cell necrosis.

The question of how long the skin-rejuvenating effect of the laser treatment lasts remains unanswered for the moment. Dams discovered that after a heat shock the gene expression (the precursor to the formation of the protein) returns to its normal level after 48 hours. However, the extra collagen produced as a result of the increased gene expression contributes to skin rejuvenation for a longer period.

Although this study suggests that it is heat rather than light that rejuvenates the skin, the laser still remains the instrument of choice in the opinion of Dams. "A laser allows treatment with great precision, because it can specifically heat specific elements in the skin while leaving the rest unharmed. This allows the optimal effect to be achieved."

Dams conducted her research in cooperation with Philips Research Eindhoven.

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Genetic Predisposition to Certain Skin Cancers May Be Associated With Vitamin D Deficiency

ScienceDaily (Oct. 20, 2010) — Patients with basal cell nevus syndrome, which predisposes them to develop non-melanoma skin cancers, appear to be at increased risk for vitamin D deficiency if they take steps to protect themselves from sunlight, according to a report in the October issue of Archives of Dermatology, one of the JAMA/Archives journals.

"Vitamin D deficiency has been associated with an increased risk of auto immune disease, fractures, cancer, cardiovascular disease and all-cause mortality," the authors write as background information in the article. "There is increasing concern that sun protection, recommended by dermatologists to prevent further UV damage in populations susceptible to skin cancer, may result in abnormally low levels of 25-hydroxyvitamin D [25(OH)D, a blood measure of vitamin D levels], which may have subsequent detrimental effects on health."

Jean Y. Tang, M.D., Ph.D., of Stanford University Medical Center, Redwood City, Calif., and colleagues studied 41 patients with basal cell nevus syndrome, who are genetically predisposed to develop basal cell carcinomas. Individuals with this condition usually develop multiple basal cell carcinomas in young adulthood, as opposed to most cases of sporadic basal cell carcinoma, which occur in the sixth to seventh decades of life. Patients with basal cell nevus syndrome generally try to prevent skin cancers by using sunscreen and avoiding the sun during peak hours.

The 41 patients had blood drawn an average of three times during the two-year study; 23 (56 percent) were vitamin D deficient. When compared with the general population, patients with basal cell nevus syndrome had lower average vitamin D levels and were three times more likely to be deficient.

Blood vitamin D levels were lower among patients with basal cell nevus syndrome who were overweight, and in those who had blood collected in the winter compared with the summer.

Among 35 patients with basal cell nevus syndrome who completed a survey, 28 (80 percent) reported using sunscreen daily and most reported avoiding sunshine during the hours of 10 a.m. and 2 p.m. "It may not be surprising that patients with a genetic predisposition to sun-induced cancers report a high frequency of photoprotection and may be vitamin D deficient," the authors write. "However, the magnitude of this deficiency and the possible additive effect of obesity, which is common in these patients, make individuals with basal cell nevus syndrome optimal candidates for cholecalciferol supplementation."

"Furthermore, if the mechanism for the association between low 25(OH)D levels in patients with basal cell nevus syndrome is indeed photoprotection, these results may be applicable to patients without basal cell nevus syndrome who have sporadic basal cell carcinomas and for whom photoprotection is currently recommended," they conclude. "Given that sporadic basal cell carcinoma is the most common cancer worldwide with more than 1 million cases reported annually in the United States and that most patients with basal cell carcinoma survive for many years after their diagnosis, screening for vitamin D deficiency may become an important part of the care of this population."

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