Iodides and bromides are drugs that can cause severe adverse cutaneous reactions, and of these, the worst are acneiform, furuncular, carbuncular, chancriform, pyodermatous, or granulomatous. Iodides and bromides are widely distributed, not only in foods and in the environment but also in proprietary and formally prescribed medicaments. These figures are of still relatively minor consequences of adverse reactions from the two halides, of which bromides are usually worse than iodides. Lesions like those of acne or folliculitis caused by an iodide are shown in Fig. 18-10. Figure 18-11 is a granulomatous reaction caused by a bromide. Another baleful characteristic of drug eruptions from halides is persistence and extension of reaction once it occurs. The reason for such persistence or extension, even when a known source of the offending drug is removed, is the wide dispersion of occult iodine or bromine salts in foods, in the environment, and indeed in the body's own chemistry. Iodine, for example, is a constituent of thyroid hormone.