Onychomycosis is a common nail disease, responsible for up to 50% of diseases of the nail. The distribution of different pathogens is not uniform; it depends on various factors such as climate, geography and migration. However, studies have revealed that two dermatophytes, Trichophyton rubrum and Trichophyton mentagrophytes, account for more than 90% of onychomycoses. Onychomycosis can be divided into four major clinical presentations: distal subungal (the most common form of the disease), proximal subungal (the most common form found in patients with human immunodeficiency virus infection), and superficial and total dystrophic onychomycosis. Onychomycosis is a multifactorial disease. Age has a very important effect on the occurrence of onychomycosis, with a correlation between increasing age and infection. Genetics has also been identified as a factor governing the epidemiology of onychomycosis; T. rubrum infection shows a familial pattern of autosomal dominant inheritance. Disease and lifestyle may also play a role in the epidemiology of fungal nail infections. Studies have shown that diabetes, acquired immunodeficiency syndrome and peripheral arterial disease may be independent predictors of onychomycosis. Because of the multifactorial nature of the epidemiology, accurate diagnosis, pertinent treatment and patient education must be paramount when treating the disease.

In earlier skin pharmacokinetic studies we have shown that terbinafine is rapidly delivered to the stratum corneum, nails and hair both through sebum and by direct diffusion through dermis-epidermis. In the present study the skin pharmacokinetic profile of terbinafine was studied in two groups of eight human male volunteers during and after 250 mg orally once daily for 7 and 14 days. In the 7-day study high terbinafine levels were found in sebum (19.0 micrograms/g) and stratum corneum (2.5 micrograms/g), and a concentration in stratum corneum above the minimal inhibitory concentration for most dermatophytes was still found 48 days after the last day of medication. Terbinafine was found in peripheral nail clippings after 7 days of medication and the concentration was, in the 7-day study, 0.5 microgram/g 1 day after stopping medication; it was still 0.2 microgram/g 90 days after stopping treatment. The results in the 14-day study were in parallel with, but higher than, in the 7-day study. The elimination of terbinafine from several compartments is biphasic, with a faster initial elimination followed by a slower secondary elimination. For nails, the elimination is slower compared with the other compartments. The results indicate that terbinafine may be effective in short-term treatment of several dermatophytoses. The concentration of 0.2 microgram/g of terbinafine found in nails 90 days after stopping medication, following 7 days of treatment, indicates that the duration of therapy, even in tinea ungium, may be shorter than is currently the case.

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Bathing is generally superior to washing, provided basic safety procedures are followed, and has psychological benefits for the infant and parents. When bathing infants with a liquid cleanser, a mild one not altering the normal pH of the skin surface or causing irritation to skin or eyes should be chosen.