By pyro I assume you mean pyrogallol and not pyrocatechin (catechol). The problem with this developing agent is its high toxicity. The LDLo, lowest lethal dosage is only 28 mg per kilogram of body weight. This chemical attacks the liver, kidneys, bone marrow and nervous system. In addition it is easily absorbed through the skin from its solutions. The toxic effects are also cumulative. When working with the solid, a respirator, goggles and nitrile gloves are mandatory.
Let me put the toxicity of this chemical in perspective. The great mystery writer Agatha Christie was an authority on poisons. She wrote a book about them. Her favorite means of dispatch in her books was arsenic usually in the form of the trioxide. This chemical has a LDLo very close to that of pyrogallol.
If a staining developing agent is desired I would suggest using catechol, which is less toxic.