It’s been standard in the past for nail strengtheners to incorporate formaldehyde into their formulations. But increasing public concerns about formaldehyde has caused Nail Tek to rethink. Using natural aldehydes, Nail Tek has developed a process that duplicates its strengthening power while removing formaldehyde and substituting a naturally occurring alternative derived from citrus sources. This natural aldehyde is non-toxic and no skin or nail reactions have been reported. CITRA Formaldehyde Free by Nail Tek has been proven clinically effective in strengthening nails, says the company.