Work at the University of Derby and at University of Central England in the UK showed that 'Tea tree oil and lavender oil, when used in isolation, demonstrated unequivocal fungicidal activity' against Trichophyton rubrum. T. rubrum is the culprit in around 80% of fungal nail infections, it invades keratinized tissues and produces a yellowed nail that is thickened and brittle. Lavandula angustifolia was used.