The MSDS safety sheet list hydroquinone as a toxic agent. To quote,
Originally Posted by Deckled Edge
"Probable carcinogen. Toxic. Severe skin irritant. Harmful by inhalation and ingestion. May cause sensitization. Eye and respiratory irritant."
The MSDS sheets indicate that pyrogallol is more of a risk, but the difference is not as great a s some people believe. Chemically the two agents are very similar. People do appear to be more aware of the risk of pyrogallol and pyrocatechin than other reducers, which may be due to the fact that the people who promote developers based on these agents have taken a responsible position and warned of the health risks.
Bear in mind that sensitization to a chemical normally results from long-time use, and once you become sensitized it is for life. I worked for many years on a boat-building project with epoxy and would frequently get it on my hands. I had no problems at all for years and years, but one day after some got on my hands I developed a severe rash, with many visible bumps, on my forehead and fingers. Every since then any contact with epoxy, or sometimes just the smell alone, causes eruptions of the same type and in the same place. I think anyone dunking their hands in developers that contain reducers such as hydroquinone and metol run the same risk of sensitization.
People who insist in not using gloves with tray development should consider switching to one of Patrick Gainer's Vitamin C formulas. My understanding is that ascorbic acid is about as safe a reducer as you can find.