The knowledge of the chemical composition of the most commonly used pigments is necessary for the diagnosis of some cases of contact eczemas caused by tattoos. Several techniques of chemical analysis and characterization were used to study the materials involved in a permanent tattooing process such as pigments, solvents, needles and specially in the metals contained in them. A battery of patch tests is proposed that includes some substances characterized in the analysed pigments.
Skin care companies try to find the best way for cutaneous hygiene in defective skin conditions. Novel strategies to ensure extra-mild non-soap surfactant cleansing products should be searched for and designed. Among possible strategies, the control of the physicochemical behaviour of surfactants in solution seems to be a promising approach to minimize their irritant properties. To assess this, we have tested – with 28 healthy volunteers by means of 48-hour patch testing – the irritant capacity of the following solutions: sodium lauryl sulphate (SLS) 1% w/w, disodium cocoyl glutamate (SCG) 1% w/w, sodium PEG-4 lauramide carboxylate (SLC) 1% w/w and the mixtures SLS 1% w/w + SCG 1% w/w and SLS 1% w/w + SLC 1% w/w. The cutaneous responses were evaluated by visual scoring and bioengineering measurements of transepidermal water loss, laser Doppler cutaneous blood flow and skin colour reflectance. The experimental values of all bioengineering end-points and visual scores have shown that the addition of co-surfactants to a constant dose of SLS produces a significant reduction of skin irritation notwithstanding an increase in the total surfactant concentration. The physicochemical studies show that the control of the physicochemical behaviour of surfactants in solution could be a promising approach to develop cleansing products with a less damaging effect on the skin.
Propylene glycol (PG) has been described as responsible for contact allergy and irritant reactions, but there are a lot of non-conclusive studies reporting a different percentage of patients irritated, with diverse concentrations and doses applied. As this substance is contained in a large amount of products, we reviewed its irritant capacity and the appropriate concentration to be tested. PG from two different origins was tested in 230 healthy volunteers. We applied 25 µl of PG at two different concentrations (70 and 100%). PG from origin B (PGB) was tested furthermore with two different qualities. Biophysical measurements were performed in those subjects patch-tested with PGB and its acute dermal irritation was tested in human skin culture. After 48 h results did not show any difference between PG from both origins and qualities. After 96 h PGB was slightly more irritant than PGA. Biophysical measurements only increased significantly in the subjects with a positive allergic reaction and there were no differences in the in vitro test. PG is not valid as pattern of irritation even at 100% concentration because it irritates a small percentage of patients. The recommended concentration should be between 30 and 70% in water, and the 100% concentration could be used in non-reactive patients.
