Should doctors be allowed to prescribe placebos for their patients?

There seems to be a lot of evidence suggesting that placebos do actually work. For example 2 sugar pils are better than 1 for healing stomach ulcers Blue sugar pills are better than pink ones for treating anxiety. Putting a brand name on the packet of sugar pills improves their ability to treat pain.

Ethically there is a bit of a problem because you cant actually tell the patient you’re giving them sugar pills else they wont believe they’ll have an effect.