An antimicrobial agent, hiba oil, was examined for contact allergenicity in a modified guinea pig maximization test. Hiba oil produced weak contact allergenicity by intradermal injection dose at ≥5, 000ppm and challenge doses at 5, 000ppm. Even at the highest intradermal dose of hiba oil (50, 000ppm), only half of the animals showed a positive skin reaction to the challenge patch of hiba oil at 5, 000ppm. Two antimicrobial components of hiba oil, hinokitiol and carvacrol, were not the critical substances of allergenicity, as these chemicals failed to cause positive skin reaction in a cross-sensitization test.
A new product consisting of nanoscale particles of platinum (Pt) embedded in the surface of a rutile form of titanium oxide was manufactured by the faculty of science of Osaka City University. Titanium oxide (TiO2) has photocatalytic activity that generates superoxide and hydroxyl radicals. Experiments were performed on Escherichia coil A3-4 and Staphylococcus aureus 209p to evaluate the antibacterial effects of TiO2 carrying nanoscale particles of Pt and of three other commercial kinds of TiO2 under fluorescent lamp irradiation. To compare, experiments were conducted under the same conditions on four copper compounds, whose antibacterial effect depends on solubility. The antibacterial effect of TiO2 carrying nanoscale particles of Pt may result from photocatalytic oxidation and Pt. It is difficult to compare the bactericidal effects of copper compounds and titanium oxide as their solubility in water is very different. 0.4mM of copper sulfate was completely dissolved and killed bacteria completely. While 0.1g/ml of titanium oxide killed bacteria completely, the required levels of Ti and Pt dissolved in saline water were 6ppb and 23ppm respectively.