What characteristic must ointments possess to be effective at body temperature?

Ointments must be soft enough to spread at room temperature and melt at body temperature to ensure their effectiveness. This characteristic is crucial because ointments are typically used to deliver medication or provide relief to the skin and underlying tissues.

When applied at room temperature, the ointment should easily spread over the skin without being too hard or rigid, which would make application difficult and uncomfortable. Once the ointment comes into contact with the warmer temperature of the body, it needs to melt or soften further. This allows the active ingredients to be adequately absorbed into the skin and enhances their therapeutic effect.

In contrast, if an ointment were tough and rigid at room temperature, it would be challenging to apply and distribute over the skin's surface. If it remained solid at all temperatures, it would not be able to fulfill its intended purpose of delivering medication effectively. Immediate absorption into the skin is not a necessary characteristic for all ointments; rather, they work by gradually releasing their active components, often providing longer-lasting effects.