Sclerotherapy is the "gold standard" and is preferred over laser for eliminating telangiectasiae and smaller varicose leg veins.[12] A sclerosant medication is injected into the diseased vein so it hardens and eventually shrinks away. Recent evidence with foam sclerotherapy shows that the foam containing the irritating sclerosant quickly appears in the patient's heart and lungs, and then in some cases travels through a patent foramen ovale to the brain.[13] This has led to concerns about the safety of sclerotherapy for telangectasias and spider veins.