Calamine information from DrugsUpdate  

Calamine is a mixture of zinc oxide (ZnO) with about 0.5% iron(III) oxide (Fe2O3). It is the main ingredient in calamine lotion and is used as an antipruritic (anti-itching agent) to treat mild pruritic conditions such as sunburn, eczema, rashes, poison ivy, chickenpox, insect bites and stings. It is also used as a mild antiseptic to prevent infections that can be caused by scratching the affected area, and an astringent to dry weeping or oozing blisters and acne abscesses.

List of Contraindications