Almost any substance, natural or artificial, can cause a reaction in someone somewhere. Everyone is different and you might find yourself responding to something that thousands of others would easily use. For example, some people are allergic to wheat and others are not. Sistaco nail products are intended for the nail plate and not for the skin. Reactions are very rarely caused by applying the product as it should, but by contact with the skin before exposure. If our product gets on the skin, it should be removed immediately with a damp cloth or wipe. Do not use on damaged nails. While unfortunate, a reaction does not mean the product is unsafe for the general population and all of our products are federally recognized as safe and non-toxic. In the extremely unlikely event that a user experiences a mild reaction, please remove the product immediately and discontinue use. Most reactions to a product are very minor and quickly disappear on their own after use has ceased. All our products are tested and comply with global cosmetic standards.