Peanut Allergy and the Skin: Q&A with Dr. Helen Brough
November, 2014 – The skin may hold the answer as to why some children develop peanut allergies before they’ve even eaten a single peanut, suggests new research.
Dr. Helen Brough is the lead author of an influential 2014 British study that reveals how exposure to peanut residue in household dust can increase the risk that children with eczema or other skin conditions will go on to develop peanut allergy.
Allergic Living interviews Dr. Brough but first, some background on the study:
- Researchers vacuumed sofas in the homes of 577 U.K. babies in their first year of life.
- Detectable peanut protein was found in more than 1/3 of the dust samples.
- Years later, at ages 8 and 11, the children in this same study group were tested for peanut allergy, as well as mutations of the FLG skin gene (such mutated genes are strongly associated with eczema).
- Of those who had become peanut-allergic, 1 in 5 had the mutated FLG gene.
- In homes with 3 times as much peanut in the dust, a child with the mutated gene was 3 times more likely to develop peanut allergy.
“Previously it was thought that children developed a predisposition to becoming peanut allergic by exposure to peanut from maternal peanut consumption during pregnancy or breastfeeding,” explains Dr. Brough, an honorary senior lecturer at King’s College London. “This study suggests that there may be an alternative route by which children might develop become peanut allergic – and that is through exposure to peanut through the skin.”
In the following interview with writer Ishani Nath, pediatric allergist Dr. Helen Brough discusses the groundbreaking study and what it could mean for our understanding of how peanut allergies develop.
Allergic Living: What is it about the skin and its immune system that is leading to allergy?
Dr. Helen Brough: In children with porous skin (due to FLG mutations) allergens are thought to penetrate the skin and predispose the body towards an allergic response. There is evidence that disruption of the skin – through constant scratching, irritation or inflammation – leads to an allergic immune response in the skin. Peanut could therefore penetrate disrupted skin when the immune system is predisposed towards allergy, and lead to a peanut-allergic response.
Infants in the study who did not have the mutated FLG gene were safe from the effects of peanut proteins in household dust.
AL: How does peanut protein get into household dust?
HB: Peanut can be measured on hands and in saliva at least three hours after eating a peanut-containing meal. Thus, peanut can be transferred into the environment by hands or saliva, for example onto bedding while asleep, for some time after eating peanuts.
AL: If you don’t eat peanuts in your home, will there still be peanut protein in your household dust?
HB: In our study, peanut protein was found in the dust of the infant’s bed and play area in about 10 percent of homes where there was no or minimal household peanut consumption. This may have been due to other friends and family visiting the home who did eat peanut.
AL: Can regular cleaning methods effectively remove peanut proteins from the home?
HB: Although peanut levels in the environment were not removed completely after routine cleaning, a significant reduction was achieved. Peanut levels in dust were reduced 1,000-fold from sofa covers and 40-fold from pillows using a single machine wash at 60º C with laundry soap.
Peanut protein levels on table surfaces were also reduced by cleaning with detergent. On granite tables, cleaning with detergent completely removed detectable peanut but, on wood tables, cleaning did not completely remove peanut. Thus, the type of table surface also affects the efficiency of removing peanut from the environment.
AL: What should parents of infants with atopic eczema (or otherwise damaged skin) do to help avoid the development of peanut allergy?
HB: We would recommend good treatment of eczema, using enough moisturizer to protect the skin barrier (500 grams of moisturizer per week).
The results from this study are not conclusive as they only show an association between high levels of peanut in the homes and an increase in peanut allergy in later life. In order to show that high environmental peanut levels lead to peanut allergy, a study would be required where environmental peanut levels were reduced in one group of children with eczema versus continuing as before in another group. Thus, no recommendation can be made to parents at this time.
The Learning Early About Peanut (LEAP) study is assessing whether early peanut consumption (from four to 11 months) may protect the child against developing peanut allergy. These results will be available in 2015. [Editor’s note: see our LEAP study article from February, 2015.]
AL: What do these results mean for the future of how we prevent or treat peanut allergies?
HB: It may be that the timing and balance of skin and oral exposure to a particular food early in life determines whether a child develops an allergy or tolerance to that food. This study aims to prevent peanut allergy from developing in the first place, as once a child has peanut allergy there is an 80 percent chance that they will not outgrow this. There is other work assessing how to treat peanut allergy using peanut desensitization.
AL: What are the next steps for this research?
HB: In order to show that high environmental peanut levels lead to peanut allergy, a study would be required where environmental peanut levels were reduced in one group of children with eczema versus continuing as before in another group.
Related Research: A Consortium for Food Allergy Research (CoFAR) study examining the relationship between exposure to peanut in household dust and the development of peanut allergy was published in November 2014 in the Journal of Allergy and Clinical Immunology. This study also finds a strong connection among household dust, eczema and the onset of peanut allergy.
While both new studies are opening the door to exciting new information about how food allergies develop, Dr. Scott Sicherer, lead investigator with the Icahn School of Medicine in New York, cautioned that more research is needed before recommendations can be made. “We need to see if early interventions, such as earlier food consumption, improving the damaged skin barrier, or reducing household exposure will counter the development of the allergy,” he said. Read more on the CoFAR study here.