Hypothyroidism is a serious endocrine disorder emerging from deficient production of thyroid hormone (thyroid gland agenesis or dysgenesis, or inborn metabolic defects of thyroid hormone production) or a defect in thyroid hormonal receptor activity. Prevention of iodine organification by means of using iodine-containing drugs or solutions is a protective mechanism for the body and is known as the Wolff-Chaikoff effect. This effect blocks thyroid hormone generation and is often transient, with thyroid hormone synthesis recovering in a few days or weeks. We present a neonate with transient thyroid dysfunction resulting from topical exposure to iodine-containing antiseptic solution. Our aim was to increase awareness that the use of antiseptic iodine solutions in neonates may result in transient hypothyroidism through the Wolff-Chaikoff effect and should be considered after the use of iodine-containing solutions or drugs. © 2006 Elsevier Inc. All rights reserved.