The flaky inner layer of oyster shells provides the calcium used in this homeopathic remedy, also called Hepar sulf. and commonly known as calcium sulfide. Once an antidote for mercury poisoning, Hepar sulf. is now used by homeopathic physicians to treat patients with conditions that tend to be infected, often producing pus. These disorders are accompanied by symptoms that include mental and physical hypersensitivity and an intolerance of pain and cold. Finely ground oyster shell and sulfur are mixed together and then heated in an airtight container. The resulting powder is dissolved in hot hydrochloric acid, then combined with lactose (milk sugar) in a pharmaceutical process of dilution called trituration. Hepar sulf. is mainly used when there is an infection, for example, in tonsillitis, earache, and skin complaints where the skin is sensitive to touch, moist, and suppurates easily. This remedy helps expel pus, such as in infected pimples in acne, or boils that are very sensitive to touch and ready to burst. It is also given for the following: sore throat with ear pain on swallowing and loss of voice or hoarseness; sinus congestion; ulceration or inflammation of the eyes; cold sores and mouth ulcers; colds that start with an itchy, tickly throat; a dry, hoarse cough or a crowing cough with loose, rattling phlegm in the chest; a chesty cough brought on by exposure to cold air, and flu with a fever, sneezing, sweating, and a need for warmth. When ill, people helped by this remedy are very sensitive-to cold air, touch, pain, and any kind of .disturbance. All of their bodily secretions, such as urine, perspiration, and stools smell sour. They are anxious and irritable, with unreasonable likes and dislikes, and tend to be hasty and to take offense easily.