Pityrosporum ovale in healthy children, infantile seborrhoeic dermatitis and atopic dermatitis.

The occurrence of Pityrosporum ovale was studied in healthy children, children with infantile seborrhoeic dermatitis (ISD) and in patients with atopic dermatitis (AD). Twenty children with ISD and twenty healthy infants were subjected to culture for P. ovale. Positive cultures were found in 18 of 20 infants with ISD, compared with 4 of 20 controls. The same culture medium containing olive oil as one of the lipids was used to evaluate the frequency of positive P. ovale cultures in 60 patients with AD, 40 patients with rhinoconjunctivitis and/or asthma (RA) and 40 children and young adults with no atopic history (HC). The results of the quantitative cultures from the forehead did not differ between the groups. P. ovale cultures were positive in 0-20% of children aged 0-10 years and in 60-90% of the 11-20-year-old subjects. Positive P. ovale cultures were found in 87% of 138 healthy children aged 2 months to 15 years when cultures were performed on a medium containing whole fat cows' milk as one lipid source. The largest number of colonies was found among children aged 2-23 months and among children older than 9 years. The occurrence of specific IgE antibodies to P. ovale was evaluated with a skin prick test (SPT) and RAST and compared in 3 groups (AD, RA, HC) of patients aged 0-20 years. Specific IgE were found most often in patients with AD. In patients with AD on different parts of the body, 15% had a positive SPT to P. ovale. In another group of patients, aged 14-53 years, with AD localised mainly to the head and neck area, the SPT was positive in 55% of the patients. Sera from 13 patients with positive SPT to P. ovale were further analysed with IgE immunoblotting using both P. ovale and C. albicans antigens. Simultaneous IgE-binding to both these yeasts was found in 5 sera and these were analysed with RAST-inhibition. Cross-reacting IgE antibodies to P. ovale and C. albicans were found in two of these sera. Cross-reacting sera were pooled and used as an IgE probe in crossed radioimmunoelectrophoresis and Tandem-crossed immunoelectrophoresis. Cross-reacting epitopes were suggested to be located in the mannan polysaccharide of C. albicans and in a high molecular weight fraction of P. ovale.(ABSTRACT TRUNCATED AT 400 WORDS)