there are several researches that explain the efficacy of using aluminum foil or white cloth at the sides of phototherapy unit, or even covering the incubator (for infants in incubator). here are the websites: http://www.ncbi.nlm.nih.gov/pubmed/6714261?dopt=abstract http://www.ncbi.nlm.nih.gov/pmc/articles/pmc2672760/ http://www.nejm.org/doi/full/10.1056/nejmct0708376#ref35#t=citedby and there's a research that shows that turning of infants during phototherapy for hyperbilirubinemia doesn't increase its efficacy. >> http://www.ncbi.nlm.nih.gov/pubmed/11948386