All materials used have been extensively tested and fulfill all relevant regulations, including the EU Nickel Directive. Our Silicon and PU straps do not contain any phthalates. Allergic reactions to GUL watches are exceedingly rare, in fact we have only heard of a few cases in more than 35 years and among 2 million sold watches. Our famous Micro watches have titanium case backs to further reduce the risk of over time buiding up a sensitivity to allergens.