It is important as it prevents selection bias affecting which patients are given which treatment (the bias randomisation is designed to avoid). Allocation concealment is possible with all types of trial, including unblinded trials, and is therefore universally recommended.

What is the difference between concealment and blinding?

The key difference is that allocation concealment is done before/along with randomisation, while blinding is usually happened after randomisation.

What is concealment in epidemiology?

Allocation concealment is a when the person (or system) responsible for allocating people to different treatment groups and control groups: Doesn't know what the next treatment allocation will be and. Conceals the results of the allocation from others.