Eye, ear and nasal drops are sterile aqueous or oily solutions meant for instillation into respective areas. Eye drops contain drugs that are antiseptic, anesthetic, anti-inflammatory or cause pupil dilation/constriction. Ear drops and nasal drops contain medications to relieve conditions like congestion. All three include active ingredients, vehicles, preservatives and adjuvants in suitable containers. They must be free of particles, sterile, have proper pH, tonicity, viscosity, surface activity and not cause irritation. Thickening agents, isotonic solutions, and surfactants are added to meet these requirements.