Almost any substance, natural or man-made can cause a reaction to somebody, somewhere. Everybody is different and you could find that you have a reaction to something that thousands of others would use without any problem. Some people are allergic to wheat for example and others are not. Sistaco nail products are designed for the nail plate and not for the skin. Reactions are very rarely caused by the product being applied as it should, but by contact with the skin prior to being set under light. If our product does go onto the skin it should be removed immediately with a damp cloth or wipe. Do not use on damaged nails. Although unfortunate, a reaction does not mean that the product is not safe for the general population and all of our products are government approved as safe and non-toxic, not containing the 16 harmful chemicals often found in nail formulations. In the extremely unlikely circumstance that a user has a slight reaction, please remove the product immediately and discontinue use. Most reactions to any product are very minor and will clear up by themselves quickly after usage is stopped. All our products are tested and are compliant with worldwide cosmetic standards.