Almost all photographic developers contain hydroquinone, which is irritating to eyes and skin. Most also contain metol which can produce an extreme sensitization in some individuals, producing painful and dangerous dermatitis. Phenidone, developed by Ilford and still mainly used in their products, is a safer alternative. Developers may also be a danger because of their high pH - they may well be sufficiently alkaline to cause eye damage, and safety glasses are recommended. Splashes of developer in the eyes should always be washed out immediately with plenty of running water.
Most developers are both toxic and caustic.
Some still contain the developing agent 'Metol' which can cause a painful and dangerous skin irritation in those who become sensitive to it - 'metol dermatitis' is a recognised industrial illness. Dektol gives cold to normal tones. Kodak D163, a useful warm tone developer, is now in the public domain, but it is cheaper to buy the mixed powder ready for use unless you buy raw chemicals in very large quantities. Their powder form Bromphen is also a phenidone developer and Ilford recommend this for processing their warm tone paper. Ilford also produce a Multigrade developer that appears to have no real advantages over their PQ developer.